Concept: Champ whose gimmick is his second bar stores power as he's damaged.
Play style: Tank who times abilities to get da massive damages.
Ideas: Passive gives bonus health? Increases healing? Probably increasing regen and healing recieved so he is useful in lane without being too survivable for a masochist champ. Second bar is limited to 10%(?) HP so you can't stack up absurd damage and if you get bursted down the bar is wasted as you're not getting extra damage.
Q- Makes you less tanky for a couple seconds so you fill up the bar faster? Maybe alternates between extra tanky or way less tanky so you get the bar filling up at different speeds.
W- Damage spell where you deal the bar's damage plus an increasing amount of missing hp?
E- ~~Dash~~ No. I dunno, ideas? Probably another damage spell, one that heals?
R- Freezes Hp, but you still take the damage eventually. The bar fills up normally but the damage is not taken immediately. Instead it hits you after 5/8/whatevs seconds. Maybe it could work like that item that bleeds 15% of the damage onto you? Maybe to prevent backdoor exploits it could be made to only freeze HP when you're taking champ damage or enemy champs are nearby?