Tryndamere New Ultimate
I think that, in order for Tryndamere to be good, his ultimate needs to be more counterable yet still serve the same purpose. So, this is my take on a new one:
Ultimate- Undying Rage Active: For 5/5.5/6 seconds, Tryndamere reduces all forms of damage taken by a flat 50/100/150 plus 60/80/100% AD. This can reduce damage taken down to 0. Tryndamere also gains 50/75/100 Fury upon activation. This can be activated during crowd control (this is not a new effect).
Some form of mega shield that can still be pierced but to most forms of damage still makes him immune to death.
and 
, but it never gets REDUCED. Or else it wouldn't be true damage, that's what it means, damage that isn't mitigated by armor, magic resist, or anything else.