Parked my last Stellaris game after I basically won (Galactic Emperor, smacked the Contingency, and enough fleet power to walk over anyone who even looked at me funny). Almost thought I managed to make the Unbidden spawn, but seems Ultima Vergilis just is being ominous when you already beat the crisis, shame.
Started a new game and since I usually turtle I figured I'd force myself into early combat by going at is as a Driven Exterminator Gestalt Consciousness. Only to spawn between two Fallen Empires and another Driven Exterminator. Great.
Also ended up running into some major Trade deficit issues because I'm not familiar with how to play machines, so ended up mostly turtling anyway while I figured out/fixed my economy. At that point one of the Fallen Empires decides to awaken, and since I can't handle them in a fair fight I build up fortress systems and fleets like mad and shelve any plans for wanton galactic murder sprees.
Aaaand then Cetana decides to spawn, obliterating the FE(s), taking some of my (fortified) systems with her and then just basically ruining the rest of the game (as far as I'm concerned). All the research options for the crisis end up outside my borders, so unless I want to fight a whole load of wars to get to them I have no access to them. So I have content myself with nabbing her transports, trying to get somewhere with the situation that way. Unfortunately she somehow goes hostile before she declares war somehow, despite me having "good" rep (bug?) and just "removes" some of my biggest fleets (not even combat, just dialogue and *poof* fleet gone...).
Once she finally does declare war I try beelining her with everything I have left but just get smacked like a fly. She, herself, has 1.5m fleet power, and the rest of the crap in the system she hides in counts for another million or so, even before losing a bunch of ships to bs I managed only like half that.
AI doesn't even try to deal with her, like at all, unlike every other crisis where at least they can act as a distraction. Might as well be alone in the galaxy for this one, and can't rely on Fallen Empires to do, well ... anything as she just outright murders them with a 100% guarantee when she spawns.
This is also where I learned you can't disable a specific crisis, you can pick a specific one, but you can't say "give me any random one, except for that one", which is annoying as from what I've seen I don't think I want her in most of my games (but I don't necessarily want to disable the whole DLC) as she seems ridiculously over-tuned compared to every other crisis (and I just generally dislike things being on timers like this).