Do other endgame crisis appear if I am already the crisis?
In the new expansion for Stellaris, Nemesis, the player can become the endgame crisis.
I wanted to know if the AI endgame crisis will still spawn if I have already become the endgame crisis?
According to the forums, yes, an endgame crisis can still occur after you (or an AI, or both) Become the Crisis.
Completely intended that player (or AI) empires taking the ascension perk doesn't stop the end-game crisis from spawning.
Other reports in that thread indicate that other crises still occur too (the Khan, the War in Heaven, etc.).