Disclaimer - I do not own any of the characters mentioned in this story aside from Suicidal who is my original character. Otherwise I would be very, very wealthy.
Just a very rough scene by scene go through from the Avengers movie combined with an OC of mine.
As Nick Fury walks down to the holding area where the tesseract is being operated he is followed by two women and calls to one of them "So Hill tell me what's up". Maria Hill replies "We have reports that the tesseract is malfunctioning. Dr Selvig is on it but there's no telling what could happen". "Sounds fun" replies Nick Fury and signals over to the second woman and says "That's why I brought my bodyguard here". There stands a stern and modest looking slender woman of average build with short dark hair and she nods in reply. "Agent Sarah Jensen, stay on alert something serious might be going down" adds Nick Fury.
As they approach the tesseract they notice Dr Selvig near the cube and Nick asks "Dr Selvig. Any news". Dr Selvig nervously replies "I don't know what to do Nick. The tesseract, it has a mind of it's own it's acting out of it's own desire". While Selvig continues Nick Fury looks around and cuts in "Where's agent Barton" to which Selvig replies "The Hawkeye! In his nest as usual". Upon hearing his name agent Barton descends down to greet Nick Fury and his fellow agents. Nick Fury addresses Hawkeye and says "Agent Barton I told you to keep an eye on things" and Hawkeye replies "I see better from a distance".
Suddenly the tesseract comes to life and shoots out a beam across the room and there in front of everyone appears Loki. While everyone looks in shock Nick Fury commands "Put down the weapon". Immediately Loki attacks blasting an energy beam from his staff into one of the agents then leaps across the room towards Barton and Selvig paying no attention to the gunfire. Nick looks at Sarah and says "Agent Jensen you're on". Sarah pulls up her bracelet with an activation switch and immediately she begins to transform. She grows almost a foot in height, her short dark hair extends into a long red flowing mane and her fingernails grow out tearing through her gloves.
While Loki appears distracted with Hawkeye Sarah charges into Loki and launches at him with a flying kick followed by a punch and the Asgardian steps back from the impact. Loki looks at the woman and says "You dare strike Loki? Do you truly wish to die so soon", but with a smirk she replies "Do I wanna die prettyboy? Guess you haven't heard but I'm SUICIDAL"! She strikes him again but Loki deflects her punch then spins around knocking Suicidal back with his staff then blasts her away. As Loki turns around to stab Hawkeye then Selvig in the heart to take over their minds he mutters to himself "That wench survived a blast from my staff and managed to hurt me. She may be of use". With Hawkeye and Selvig now under his control Loki walks over to the recovering Suicidal and points his spear into her chest but is surprised when nothing happens.
Loki remarks "Strange. While you do possess a rather large bossum you should still fall under my control". Suicidal giggles back and says "I have very hard skin in case you didn't notice so why don't you put your little toy away". "Impudent Wench"! Screams Loki and lifting Suicidal by the throat crushing her throat. While Loki holds her up she raises her arm with curled fingers to scratch his face but Loki catches her wrist and hurls her away and immediately commands Hawkeye to shoot Fury. With Nick Fury down and the tesseract in his possession Loki signals them to move ahead. While Loki and his servants make off Maria Hill helps Fury to his feet making sure he's ok and checks on Suicidal who replies "I'll survive but you must forgive me Commander Fury, I failed in my duty to protect you". Nick Fury replies to her "Save it for later you did your best. Now lets follow".
As the three SHIELD agents follow on Loki's trail he escapes them and Nick Fury stops the car and orders the two women "Agents Hill and Jensen. I'm headed to the helicopter you two continue on to safety. As Maria drivea on she asks the wounded Suicidal if she's ok and she replies "I'm fine but I can't relax otherwise I'll shrink back to skinny me". As they continue the ground beneath them gives way and their car drops down into the ground. As both women gather their bearings Maria looks up and yells as a large slab of concrete collapses onto them. Immediately Suicidal leaps to her feet and stands over Maria as the giant slab breaks on her super tough skin and collapses around them.
Maria lookes in awe at the exhauseted Suicidal as she begins to show weakness and fatige. While she's still powered up Maria asks "Sarah can you get us out of here", and Sarah replies "Well it's not like I can fly but I suppose I can climb so I guess you'll just have to grab on". Just then Maria hears a voice through her earpiece "Agent Hill do you copy. This is Commander Fury. Report in so we can extract you".
A/N - So this is a very rough repeat of the Avengers movie with one of my original characters called Suicidal. I can't retell the movie line for line so I'm doing my best to at least make some sense. R&R please.