During versus debates, I really don't like it when the OP of the versus debate says something like, "speed equalized," or other such.
The issue with that is if you have to nerf a character's actual feats to make the fight seem more fair, then it's clear who the winner is.
Like, in a thread about who would win between Thanos from MCU or the Primarch Vulkan from Warhammer 40K, the OP said "Speed equalized."
Why did he do this? I suspect it's because Primarchs have some absolutely ludicrous feats from combat, battle tactics, strength, durability, and speed, so nerfing Vulkan's speed made the fight between the two more fair.
But, like I said, if you're nerfing an aspect of a character's feats, it's clear who wins. Vulkan blitzes Thanos, and the only outcome I can see for Thanos winning is using the Infinity Gauntlet, but even then, Primarchs have some insane feats.
Another thing I hate in versus battles is when you have multiple versions of a character and someone uses a composite version of that character without telling anyone what version of that character they're using.
Like say if we're going to debate Superman vs. Goku, then it literally depends on which version of Superman we're talking about, and what version of Goku we're talking about.
Another thing in versus battles that bothers me is when people say, "They'd work together!" but show no knowledge of the characters' personality or backstory, and in arguing this, we're missing the point of a versus battle. It's to use in-canon characters in a hypothetical fight to the death to see who would win.
Now, of course, in a different scenario, some characters would indeed work together, but in the case of Thanos vs. Vulkan, the two would engage in a fight to the death, because it'd be in character for both.
In Vulkan's case, considering that self-sacrifice to save the Emperor's subjects, no matter what (humanity and Imperial citizens) is part of the Promethean Creed, and considering the Imperium's view on xenos, Vulkan, being loyal to the Emperor, would see Thanos as a crazed xenos that aims to exterminate humanity which is all the reason he needs to engage Thanos in combat.
But the most egregious thing I've seen in versus battles is people giving characters feats that were never established in the actual canon. Sure, we can all make up a character that can beat everything, but the point of a versus battle is not to use fanon versions of characters, it's to use the canon characters in a hypothetical duel to the death. So, obviously, to determine a winner, research needs to be conducted on that character from reliable sources.