Ok here is my attempt of alternative ending (currently half of it)
It is not an exact same story because I decided that your story need an explanation how she got that chemical.
Forgive me for grammatic errors because this is not my native language.

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Hyperbunny dropped the destabilizer gun to the floor and pulled her suit down to expose her breasts. She frantically rubbed her skin and stared at her chest. Her nipples were small and pink, standing firmly erect from all the excitement.

"Damm you, what is that thing? What are you trying to do ?" screamed Bunny while trying to clean green goo from her tits.

"Don't play innocent, I know that you are trying to take away my team. I can't stand it anymore. You, big titted bimbo, Even if you have no brains, all team worships you because of those huge balloons on your chest. But this will come to the end soon because this chemical will shrink your tits to the half of their size."

"I guess it will make you flat as a desk then. You old hag"

Suddenly Novahawk 's communicator turned on.
"Incoming call from the Overlord"

"What do you want? Didn't I kick your butt enough last time and you want more?"
Communicator projected the human-sized hologram of the Overlord on the ground.

"Ha ha ha.
No, this time I got you. My plan worked even better than expected.
Stupid bimbo, what do you think you stole from my base?"

"Well, it was written "breast shrinker" on the bottle. what else could it be?" nervously replied Novahawk.

"Ha ha ha, What a fool, you fell right into my trap. This is my newest bio catalyst which will make turn your breast fat into the high explosive and blow up you along with all your base."

"You bastard. I will kill you."

"Ha ha, yea, good luck. I will kinda miss you and your friend. "

"You fool, see whast you have done? Screamed Bunny
"Damit. I just wanted to make your tits smaller"
"And you call yourself a leader."
"Enough arguing we have to do something or esle everyone will die. My chest is starting to swell"
"Dammit, your tits are now bigger than mine already and I also start feeling something," said bunny while massaging her boobs.

Novahawk frantically typed something on the computer keyboard.
"No antidote is available, there is no way to reverse the process."

"We are going to die" screamed Bunny in panic.
"Not yet, I have to kill that bastard first."

"But what we can do? there is no time left."
"I have an idea, we have to get rid of those things fast. do you have a knife or something?"
"Are you crazy? And Of course, I don't have a knife why should I?"
"Well, then there is no other choice you have to rip off my breasts with your bare hands and throw them away before they explode. With your strength that should not be a problem."
"That's insane"
"Just do it before we all die I can't hold it any longer."
"Fine you asked for it" Bunny grasped Nowahawks right breast with both arms and puled it with all force, but that was not enough.
"Fuck, Fuck, I can't"
"And where is your strength when you need it?"
"Hyper Kick" screamed Bunny while smashing her foot into Novawahks breast. The foot ripped through the flesh half way leaving everything to dangle on the piece of skin.
Now bunny had no problems to tear it away and focused on another globe which already was swollen to the gigantic size.
"Hyper Punch" screamed Bunny again as her superpowered fist hit the remaining swollen balloon which blew up into pieces and flew all over the room.
"great job. Now there is no way we will manage to collect and dispose that in time." Sarcastically grinned Noahawk just before she noticed that Bunny already had everything in the plastic bag.
"You have some problems? My superspeed it is good not only for fighting".

Bunny promptly opened a window and threw the bag with all her force.
Within few seconds it exploded with great force and big fireball while still in the air high above the ground.

"Huh, we are saved," said Bunny with relief in her voice.

"Not so fast. Your ridiculous boobs already grew twice in size as well" said Novahawk while examining at her bloody chest.

"Oh shit. Totally forgot it."