There is no reason I would ever want to a) let my opponent do even more guaranteed damage to me b) not get as much guaranteed damage as possible, or c) not heal as much as possible.
Okay, first let's get to how the shit works as it is.
Win by 1 = 15%
Win by 2 = 25%
Win by 3 = 30%
Win by 4 = 33%
First off, you NEVER want to win by 4. That's a colossal waste of meter. You're burning an extra meter for a 3% differential. That meter can be better served later in the match either for either the second Clash, or meter utility for your character. In every which way, that one meter extra you could spend to get the extra 3% can have MUCH more than a 3% difference at any time else during a match.
Winning by 2 or 3 is best, but there's no guarantee the opponent will sit there and let you do it. There's no reason to burn 4 Meters on Clash if your opponent has 1 or less meters. And if they have 2, it's still iffy. Then there's the question of a 3 to 1 matchup. Do you spend it all to guarantee as what you said is, the max amount you can get as it's always optimal. But as the opponent, I have one meter, might as well save it for later when it will make a MUCH bigger difference.
And then once the opponent hits 3-4 meters with you, now there's another issue, especially with fake Wagering around. Nothing like burning all your meter on one Clash while your opponent wastes nothing. Now they have all the resources for another if it goes down, or to simply just get that much more mileage from utility.
The few times where you're spending all your meter guaranteed is A) both you and your opponent have little meter so you might as well or B) You're in Dire straights and if you don't burn it you die guaranteed. After that it's COMPLETELY on the context of the situation.
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