Weird idea for a tryndamere mini rework
Keep him the same but change his ultimate to stacks of undying rage. So maybe he could max out at 5 stacks, and if he casts a stack, the next attack that hits him within 2 seconds will not bring him lower than 1 HP. Then his ultimate could also have a passive that gives him bonus AD based on his missing health, encouraging him to play on a knife's edge.