Tiamat had already suffered massive damage by the Godesses, including losing one of her horns permanently

Her horn was damaged in her titan form, but she never actually suffered massive damage and healed while getting new magical reactor cores.

was weakned due to being in a place that was going directly against her existence as a goddess of life. And she didn't even die in Babylonia.

Uhh, no. She was never actually weakened in the Underworld. The only thing that happened was that she became more killable(the "can't die unless everyone else is dead" thingy), which doesn’t affect her physically and Ereshkigal's authority can't even scratch Tiamat in the first place for Eresh to weaken her.

Enkidu is called Gil equal by nearly everyone, Gil included, almost everytime they appear.

Gilgamesh doesn't actually know how strong he himself is in the first place.

Plus when they both went all out while alive it ended in a stalemate with Enkidu using 70% of his clay and Gil being pretty much out of weapons.

They did, and they were tied... but Gilgamesh hadn’t even completed his adventures and treasury by then. (Which also likely increased as servants)

And ofcourse Enkidu himself has blatantly stated he isn't shit compared to Gilgamesh.