There are at least three in the Angra Mainyu fight alone, some of which occur multiple times in the single fight (coloured floor alternation, look away from Mortal Gaze, cure doom from failing Mortal Gaze, Lv150 Death). Not necessarily instant-instant but guaranteed sudden death if the player doesn't realise and doesn't take the correct steps to resolve them.
Plus Ancient Flare, Curtain Call, Behemoth meteors, dragonflies, stepping in Cerberus's goo without shrinking first, running away with the scary black circle marker in Xande's fight...
Several of those either happen quickly or do not have an intuitive solution, or at least one that can be worked out in the time you have before it splatters you.