Super-Soldier serum

You decide the only way she'll learn is through intense feeling. You've gotten significantly better at mastering your powers since you made the door disappear. It's all flooding back into you somehow. Memories of the past in fragments, visual depictions of significant events. You've met Genghis Khan, you've shaken hands with the first Eternal, you've seen Thanos on his home planet before it collapsed, and you were present when Steve Rogers transformed.

"What is that?" Black Widow's voice trembles with realization. You blink yourself out of bed and in front of her, the blue syringe you hold is glowing. "It's something to help you relax." Black Widow trains both her guns on you, before you make them disappear. Black Widow attempts to shock you with her Widow's bite, before you render her wrists bare. Black Widow attempts to even throw a punch, but you grab her wrist with immense strength and inject her with the serum. She falls to the ground in pain while muttering, "This is real."

Her body convulses and pulses with life. Her back swells first, becoming wider and thicker while her spine pops into length. Her leg and arm bones break and regrow longer. She's screaming in pain as her muscles grow and swell, ripping her suit in all the right places. Her breasts expand too, and threaten to burst from her suit. You find something amusing about another individual being this far under your heel, something beautiful in every tear she sheds. Black Widow stops screaming and goes limp. "Stand Black Widow." Her voice is still just as sexy as before, only it carries much further with her large lungs, "I don't think I can." You will Black Widow into the standing position and her head nearly hits the ceiling. Her large tits are pouring out of her suit, which is now much too small. Her hand and ankle cuffs ride all the way up to her forearm and calves. You can see the defined musculature beneath her suit, each vein popping through the leather. The bulges of her thighs and biceps have torn through the fabric and you decide to will it away.

Black Widow now has the body of a top athlete, large packs of muscle in her abdomen and thighs make her especially attractive however. Her mammoth boobs float on her steel chest, and she makes a futile attempt to cover herself before you move her hands by ****. Despite the strength she probably now possesses, you possess infinitely more. Behind you Angelica nearly drools at the sight of enhanced Black Widow, but you're not done. You tweak Black Widow's nipple and she crumbles to her knee in pleasure. You now notice the stain she left on the carpet, and the stain she's making now. Her enhanced pussy is dripping so much, it's nearly leaking. You shove two of your fingers in her muscled snatch and lift her towards the ceiling."What's your real name?" Black Widow quivers and trembles under your treatment, "My name is Natasha." You toss her onto the bed next to Angelica, "See Natasha? This is all real."