[{quoted}](name=Fluffysaurus Rex,realm=NA,application-id=3ErqAdtq,discussion-id=wPB17hxu,comment-id=000200000000,timestamp=2015-01-31T05:11:15.388+0000)
First off, your numbers are off. 175 / 350 / 525 are the stat values for Garen's ultimate.
My bad. That only means the numbers are even more in Garen's favor
Second, it's magic damage. It will go through resistances.
The point, however, would be if Garen's ultimate were theoretically true damage.
525+40% of missing HP...good god, Darius couldn't build enough AD to keep up with Garen's execute damage if it were true damage.
A (tank) build that I found from C9 Meteos had about 140 bonus AD. That means at full stacks, Darius has a potential to deal 960 true damage with a reset if it kills. Meaning on a 2000 hp target (which is not an unusual amount for an ADC), Darius will be able to kill it at half health. Garen fighting the same target, who let's say has a Mercurial Scimitar and scaling magic resistance runes (72 + 30 = 102), attempting to execute a target at half health will only deal 960 magic damage before resistance, ~480 after. Just to point out, this will not allow Garen to kill the target.
Again, you were suggesting if Garen's ultimate were true damage. I was pointing out that Garen's damage potential outscales Darius', meaning that if it were true damage, Garen's would be superior in damage output.
Also, Darius's bonus AD ratios on his execute means that he can build early damage and benefit hard from it. Darius also has more damaging abilities than Garen. How can Garen be the better executioner when Darius can deal more damage in burst form and execute from a higher health?
Because Garen wouldn't have to sacrifice defense at all in order to do the same, if not better, if his ultimate were true damage. No, he wouldn't get any AD scaling on it, but he could just play human bulwark while his ultimate would have higher damage potential.