I just found an exception to the last health survival thing on a FSC run while doing heat transfers. When I have a 15 health vitapod spike floors can bypass the last bar of health, one shoting me while I had more than one bar of health. When I drop it, it always took at least two hits if I had more than one health.

Hypothesis: the activation of sudden death is based on the amount of damage you take in a single hit relative to your current maximum health. Possibly noted in that I have never seen heavy hitters (like Trojans) bypass Sudden Death while weird, random dinky things do. Unknown if this is before or after mitigation.

Also yes, I hate the term sonic mode because you can survive more than two consecutive hits if you have enough health and/or defense.

Edited for using the wrong word.