About the cheering charm not reverting Hulk into Banner.

The anger was magically induced from the staff so it being countered by an opposite magic makes some sense.

Also, the cheering charm isn't a tickling spell, it causes an actual change in mood and when overpowered can cause euphoria.

"The Cheering Charms had left them with a feeling of great contentment." - HP: PoA

It's not a physical change but a mental one.

Also I'm not a teenager, I'm 45.

About Loki being more powerful than Harry … yes and no. Physically it's not even a question. Loki was toying with Steve in the film after all and while physically wizards are a far more resilient than normal humans (Quidditch would be a far more lethal game if they weren't) they aren't inherently stronger or faster.

Magically on the other hand … Loki's magic is very limited. It's all about illusion, mental influence, a little transfiguration and the ability to hide objects and summon daggers. He also has a cold affinity from his Jotun heritage.

Harry's magic is far greater and more versatile. In the fight in Germany, Harry was trying to capture Loki while Loki was aiming to maim or kill and Loki's own power was supplemented by the mind stone inside the scepter. Harry still held his own … magically speaking.

Harry stared warily at the laughing man on the ground, wand at the ready in case he suddenly reverted back into a troll.

"I'm ok now. The anger's all gone." The man offered in between giggles as he sat up.

"Anger?"

"Yeah. You know, the… well, the other guy comes out when I'm angry or in danger."

"That was all you?! I thought Loki had turned you into a troll! I feel I was denied critical need to know information!" Harry replied

"I'm sure it's in my profile, you were reading it earlier on deck."

Harry searched his pockets and found the shrunken information package Sitwell had handed him when he had arrived.

"I … ehm … I never actually finished reading it. I only read your cover page and then we all sort of got busy."

Banner gave Harry a half incredulous, half amused look.

Further discussion was interrupted as Thor burst into the cargo hold, looking about wildly, a look of anticipation on his face and his hammer raised.

Harry barely managed to restrain himself from blasting the Asgardian.

"Where is he, where is Banner?"

Harry silently pointed to the half naked giggling man sitting on the floor.

A look of confusion and disappointment passed over Thor's face.

"I was told he had turned into a fearsome beast that would tear apart this entire ship should he not be stopped."

"Yeah, I stopped him."

"Fury seemed to think I would be the only one possibly able to match this 'Hulk' in battle. Tell me, how did you defeat him?"

Harry could almost swear there was a slight whingeing tone to the statement.

"I … err … I made him laugh?"

Thor stared at Harry in confusion.

"I do not pretend to understand the ways of wizards. If the situation is resolved I will go and confirm that my brother is still captive in his cell."

With that, the god of thunder flew off.

"Right! We're still under attack. We should make our way back to the bridge."

Harry waved his wand and transfigured random pieces of cloth into simple clothing for Banner.

"So … magic?"

Harry nodded absently as they slowly made their way down the corridors, watching for possible attackers.

"Do you rearrange things at a molecular level?"

Harry shook his head in response.

"No. I can change things into a different thing entirely. Vegetable to mineral, inanimate to animate. One of our lessons was turning a rat into a goblet for example. And transfiguration is just one field of magic, divination, warding …"

Harry stopped his explanation as two men dressed in SHIELD uniforms turned a corner and opened fire.

Harry swished his wand causing the security gate between them to slam shut with a shower of sparks as the electronics inside fried.

A few bullets had whizzed past them before the gate closed but had missed both men.

"That was close maybe you should find a place to hide until things quiet down." Harry offered.

"No. I'm good. At least if something happens I know you'll be around to try and calm me down. Truth is I normally have a good grasp on the other guy, not sure why I lost control earlier … come to think of it, everyone was acting pretty crazy."

Harry nodded and motioned for the man to follow him down another corridor.

"That might have been Loki's plan. Turning all of you against each other using subtle mental manipulations would be his style." Harry agreed.

Harry could hear gunfire coming from further down the hall.

Signalling for Banner to hang back Harry made his way forward.

Two groups of SHIELD agents were exchanging gunfire from well defended positions.

Unfortunately, Harry couldn't tell the imposters apart from the real SHIELD agents and passive legilimency was impossible at that distance and without eye contact.

"So, what's the plan?" Banner whispered into Harry's ear.

Harry realised that one group was defending access to the bridge. Hoping he was correct in his assumption, he was about to cast a series of stunning spells at the other group when he recognised one of the defenders from Barton's memories … the leader of Charlie group.

Harry stood up from out of cover and sent a bombarda at the floor in the middle of the group sending them flying, quickly followed by a string of spells: stunning, petrification, incarcerous …

Half the opposing group was down before they could recover and regroup but by that time, the real SHIELD agents had recovered from their surprise and rejoined the fight.

"Glad you showed up when you did sir." A SHIELD agent said, approaching Harry.

"Glad to help and it's just Harry. So what should we do next."

"I was going to ask you that?" The man offered.

"I'm just a consulting detective. I'm not a SHIELD agent or a soldier." Harry replied in confusion.

The man looked at Harry with a raised eyebrow and pointed at the enemy group being secured and back at Harry.

"I don't know procedures, the ships layout … that type of thing. So what should we do now?"

The man nodded.

"The bridge was under attack but we lost comms a few minutes ago. We should go up and see if the director is safe. But there's also the VIP in the drop pod."

"Thor should already be there so let's go to the bridge."

They made their way to the bridge finding a large group of dead soldiers at the entrance.

The AGENT with Harry cried out some passphrases and received permission to enter.

The bridge was a mess. Agent Hill was bruised, bloodied and battered. There were dead or wounded agents scattered about the wreaked consoles.

Harry rushed to the first group of wounded and began using his limited repertoire of healing magic.

"Did you get anything from Barton and how did he escape!?"

Harry ignored Fury for a few moments as he worked on the wounded SHIELD agent.

"Loki being captured was always part of the plan and they had two teams planning separate rescue missions. Also, whatever they plan on doing is going to happen somewhere that has something to do with Stark."

Harry rushed to another fallen agent, a medic offering Harry information on the wounds.

"As for how he got away, I got knocked about when the whole place exploded and he scampered out a hole in the wall. I tried to follow but then found Dr. Banner playing tag with Black Widow and got a bit distracted."

Fury turned to where Banner was working, helping the medics and nodded at the man.

"Good to see you being you doctor."

The man in question waved back timidly.

"So what's the situation?" Harry asked as he moved to another injured man.

"Most of our systems are down, Stark and Rogers are trying to fix the rotors so we don't crash into the ocean."

Harry nodded.

"Thor is checking on Loki and Black Widow is hunting Barton." Harry offered.

"Sir! The drop pod has just disengaged!"

Harry quickly stood up and spun in place apparating into the containment area.

The place was a mess. Agent Coulson was on the ground lying in a growing pool of his own blood, cradling a dangerous looking weapon in his lap.

"You've … got to stop … Loki."

"Yeah! I'll get on that in a moment. Just stay quiet while I try and stop you from dying."

Harry waved his and frantically, using his most powerful healing spells.

"Vulnera Sanentur, Vulnera Sanentur, Vulnera Sanentur."

Slowly, the bleeding stopped, the wound cleared and began slowly mending itself.

"Damage is pretty severe, wish I had some potions. Couple of blood replenishers and a draught of living death would come in handy right now." Harry offered as he wiped the blood away to reveal scar tissue.

"You need rest, a blood transfusion and some essence of dittany to soften up those scars but you should live."

Fury rushed into the room at that moment with exhausted looking Black Widow.

"Barton and Loki managed to steal a Quinjet. Stark and Rogers are heading to the bridge. How's Coulson?"

"He'll probably live. He's short on blood and needs an infusion and he'll be stiff and recovering for a while. Some essence of dittany will help with the scars."

Harry looked up to see an honest look of concern and relief flicker momentarily on Fury's face.

"We're dead in the air up here. Our communications, location of the cube, Thor. I got nothing for you."

Fury addressed Stark, Rogers, Banner, Hill, Romanoff and Harry on the bridge.

"Yes, we were going to build an arsenal with the Tesseract. I never put all my chips on that number though, because I was playing something even riskier. There was an idea, Stark knows this, called THE AVENGERS INITIATIVE. The idea was to bring together a group of remarkable people, see if they could become something more. See if they could work together when we needed them to, to fight the battles that we never could."

"I wasn't brought here to find the Tesseract. It's not me you wanted, just the … the other guy."

Harry turned to Banner who seemed to be trying to reign in his anger.

"A bit of both really. You really are the best person to track down the cube but I was hoping that if things turned out for the worse, the Hulk could show us his best. Unlike General Ross, I know I can't control the Hulk but if things get as bad as I think they will and if your control is as good as I believe …"

Fury let the sentence hang and dropped heavily into his chair.

"Ok so we need to stop wasting time and get a move on. We have a few things going for us. We know that they are going to set up somewhere related to Stark and …"

"Why are you planning? We've lost. SHIELD has lied and manipulated us…"

"And what? Let Loki enslave the earth? Because a spy agency didn't tell us all it's secrets and has been building weapons?" Harry abruptly cut off Stark. "I thought you were a genius! We're still alive. While we still draw breath, we haven't lost! Steve, please tell me at least you understand this."

"Harry's right. SHIELD should have been more open with us but the fate of the world is more important than a little thing like betrayal of trust."

Fury, didn't even flinch at the accusation.

"So like I was saying, we disrupted their plans so if we move fast enough we might be able to stop the invasion entirely. Wherever they are setting this up, it has to do with you Stark."

"Stark tower. It's powered by my prototype arc reactor, all the power they'd need to initiate another portal."

Harry watched as Iron Man flew off into the distance, heading back to New York, his armor moving far faster than a Quinjet ever could.

"So what's the plan?" Harry asked as Steve and Natasha maklde their way towards a Quinjet.

"Head off to New York and stop Loki."

"You are not authorized to be here…"

Steve interrupted the young pilot. "Son... just don't."

"Hey! Wait up!"

The trio turned around to see Banner running up to them looking nervous.

"Dr. Banner?"

"Not sure I should be doing this, last time Hulk visited New York we sort of broke … Harlem." Banner offered timidly as he gingerly approached the jet.

"Hopefully we'll be able to stop Loki before he has a chance to call his army but if not …" Natasha let the comment hang for a moment.

"And you're the only one other than Stark who understands the tech so having you around might be important." Steve added encouragingly.

"Ok, I'll head off to my office to pick up a few things and then I'll catch up with Stark. I'll see you there."

Cap nodded to Harry in response as Harry vanished with a soft crack of apparition appearing a second later in his bedroom.

Grabbing his cloak and his broom, Harry hesitated for a moment his hand hovering over the locked box containing both the Elder Wand and the Resurrection Stone.

After a moment of hesitation, Harry opened the box and withdrew both Hallows.

Transfiguring his padded leather seekers gloves to hold the Elder wand under his wrist and embedding the resurrection stone over the back of his hand.

The Elder Wand felt energised and eager, resting in it's holster, as if it knew what was to come.

Harry then quickly donned some of his seeker gear hoping the slightly enchanted padded leather would offer some extra protection and then draped his invisibility cloak over his shoulders and strapped the sword of Gryffindor to his back.

The entire kit looked, amazingly enough, rather impressive, the cloak gave him the appearance of being out of shift with reality as the invisibility effect was incomplete when the cloak was not fully covering him.

Rushing out the apartment to the office, Harry found Felicity napping at her desk.

"FELICITY!"

"WHAT?! WHO!?" the girl cried as her chair fell backwards.

"Grab any money we have handy, jump on the Triumph and get as far away from New York as you can!" Harry blurted out as he helped the girl stand up.

"What? Wait … WHAT!?" she asked in confusion.

"Loki, the actual Norse god of mischief, has an alien army on the way to invade Earth. New York is going to be the front line of an alien invasion so take the Triumph and get out of here as fast as you can, fly it out of town if you have to. Be careful."

"Do you know how insane that sounds?" Felicity asked as she accepted his wallet.

"Crazier than fighting a demon who hunts you in your dreams?" Harry asked.

Not giving her a chance to react, Harry spun in place and apparated from his office to Central Park, a location he had a lot of practice apparating to.

Harry leapt onto his broom and took off in direction of Stark Tower.