After revealing the existence of aggressive gizka on Rakata Prime, motivated by fanart from @laelish, I thought I should go back to that old save, since I discovered it years ago and never fully tested things.
I'm sorry everyone, I was wrong. The gizka aren't all secretly unstoppable killing machines.
One specific gizka is an unstoppable killing machine. It's the one on the path between the beach and the temple area. I guess this gizka hasn't been noticed before since, on the path to reach it, most people logically kill every available enemy before seeing it, so it doesn't seem any different. I've tried luring enemies in other areas towards other gizka, this is the only one that attacks, and it doesn't wait to be hit, it goes on the offensive the second an enemy gets too close. It's a good thing I've played this game so many times I started deliberately making nonsensical choices, or we might never have found this.
"He's got huge, sharp- he can leap about- look at the bones!"
Guys, maybe you should leave this thing alone.
Oh, he stunned the gizka! Will it make a difference?
Sadly, the rancors can't follow me from other areas, so it can't kill one, and the other gizka won't cooperate with me.
Come on! I stunned it for you! I got swiped by those claws so we could make this a team effort! Dinner is served! Stop foraging!
I'm naming you Barriss Jr. after my other favorite adorable yellow-green thing with a shockingly high body count.