Hachiman: Japanese God of Samurai! (Warrior)

Edit: Lowered Iaijutsu's contributions by 10%, and lowered the grace period to 1 second, so one can't lazily avoid everything. Also, kinda like Vamana's ult, there is a tiny period at the end of activation that should leave him vulnerable.

Alternative Ultimate Idea: (You decide if it's better than the old one)

Showdown: Hachiman dashes forward extremely quickly, before slicing through a single enemy with one clean blow. There is a CGI effect like Ne Zha's ult, where the arena mysteriously turns into sunrise/sunset. The enemy takes the damage two seconds after the strike actually connects.

Damage: 200/300/400/500/600 (+100% of your physical power) (+40% of the enemy's missing health)

Cooldown: 90 seconds, halved if an enemy is hit but not killed.

Why halved? Because Aegis is such a ridiculous counter to this.

Inspiration: Classic (read: cheap) samurai movies, where the bad guy and the hero face off, before they both make a single slash.

With a carry's health (around 2000 late game), the ultimate, at 50% health, will deal 1000 + 100% physical power. Is this too much?

With a tank, easily reaching 3500 health, the ult, at 50% health, will deal 1300 (+100% physical power).

New ult looks cool, but other than the execution aspect of it, how does it differ from Mercury's ult?

It's like Ne Zha's dash; a simple dash with a static distance and a CGI effect, only this one has SAMURAI!

Okay. Does this damage every enemy hit, or just the first one? Could be lolzy to execute a tank in the front of a fight and have that damage carry into the rest of their team.

No, it's meant for a single target only. Remember, just think cheesy samurai flick.

Note: Does damage seem okay?