RP Combat is toxic by nature. I say that because all RP be it plot or battle or tabletop is an agreement between two or more players. Basic plot stuff, the players decide what's canon. In battles, the judge gets to decide what's canon and it's up to the players to deal with it or to rage quit. And lastly, in tabletop stuff, the dice and DM mainly decides. 

So in a fight where both players want to win, naturally, neither will agree to lose. Unless one, or both of them are mature enough to see where the fault is. But in case that isn't the case, that's why we have judges. With that being said, don't argue with your opponent. Point out the game changer you found to your opponent, if they don't agree with it, then tell the judge. If the judge doesn't agree with it, then forfiet or commence the match.

On that note, why do judges like to make players edit their post? That's why matches never finish. If a player forgets to dodge an attack, then they take the hit. If the hit was lethal, then gg. No resets, that's shenanigans. Idk if that goes on here, but many sites do that and it's not the answer. 

What makes RP battles fun and interesting is that it's essentially a game of chess as we all pretty much know. You aren't likely to win by just throwing punches and kicks. It's not impossible to win that way, just unlikely because it's basic. But if you set up something like wetting up the whole arena through the course of a fight with your water powers, then shocking it via technology in the setting, then you're likely to win if you can avoid the shock as well. That's called strategy. In the cases where strategy are involved, it's less likely for the opponent to argue. It's all about outwitting them, and they were bested. And forgetting to evade, or typing a description that wouldn't actually provide a successful evasion or block, would fall under the chess category of I fucked up and made the wrong move. Now I have to accept it. 

Players mainly need to learn acceptance and to enjoy the idea of salty runbacks (rematches) and general development within themselves. In a RP fight mainly you develop, not your character, and that's so gratifying. But as is on most sites, no one wants to lose, and the opponent that was shocked will want to edit their post, or try to justify why a shock wouldn't kill them, or BS some sort of miracle escape maneuver. When they could just say, gg, that shit wont be happening next time. I'm proud of my descriptions at least. Hey, you gotta admit that I nailed a solid hit on you, heh.

The only way to fix this is to just RP to challenge yourself more than defeating the opponent. Like any fighting game, if you expect to win most of the time, you're a fool. You're going to lose way more than you win. And naturally, there may be that one guy who never loses, but that shouldn't concern you. Especially if that's never been you. You can expect to win most of the time if you never won a few of the times or even accepted the idea of losing all the damn time. You can't skip steps. 

The goal should be to write a fun match, and to make your opponent go damn, you're a tricky bitch aren't ya. If you lose, yet accomplished that, then you won. A nice way to write a fun match is to fight seriously for every three rounds they come together to RP a cool scene for a round or two then back to fighting seriously.

All it really is just being a good sport. Take a hit, express pain in regards to that hit in every other post or so after, try to trick your opponent, work on your blend of description and fluency, and call it a day. 

Also, in regards to taking a hit, don't sleep on that idea. Taking hits are often opportunities. If someone is coming in to punch you, and you say you try to grab their punching arm, but miss and take that hit. Well then your arm logically should be close enough to grab their punching arm now. Try to grab that shit, and when they say that they moved their arm before you could grab it, tell the judge because that's not likely. If the judge disagrees with you still, then hell, fight onward or just leave. Life goes on. Or try the same trick only with better wording. Blah, blah.

Sorry for the rant