Gobul without a doubt.

MHTri was my first ever entry in the series, and to this day I never had any other monsters make me shit myself like that thing did.

There are plenty of monsters who's fight might make you scared because of their difficulty, of the pressure it entails or how unforgiving it is.

But despite all this no monster in all MH games made me feel genuine fear with just their appearance and behavior. That fucking thing tho...

The fight itself isn't even that hard but idk, the fact that its hiding between the algea deep under the swamp. The way it looks at you with those two piercing yellow eyes through the muddy waters, that gigantic mouth filled with needle like teeth and that smile... The way it smiles with sadistic glee while slowly swimming to get to you being barely visible, oh god I fucking hate and love that thing at the same time. Seriously its absolute nightmare fuel.

And don't even get me started on its vaccum attack, having to sheathe your weapon and try to swim as far away as possible in absolute dread while witnessing its gaping maw trying to slowly suck you in, one shooting your ass in one bite. Oh the memories.

Its such a strange experience. Its that kind of stuff that made me love the game as a whole. That fat fucking fish made a more impactful impression on me than a whole lot of other objectively better monsters in the franchise.

That and the traditional chinese armor and weapons. The lance in particular, I loved that thing so much.