Canada

There are fascists fighting on both the Ukrainian and the Russian side. Fascism and ultra-nationalism is not a uniquely Ukrainian issue, it is a post-USSR-space problem. However, arguably there is HUGE difference in terms of the political position of fascists and their claims to political hegemony in each country.

In Ukraine, the fascists do NOT have political hegemony. They are literally forced to obey a russophone-born Jew whose grandfather was a Red Army colonel and has family that died in the holocaust. Electorally they have been ridiculously small, at small single digit numbers. Even with the booster shot that Putin conveniently gave them by making heroes out of them, Ukrainian society has not embraced them and Ukrainian institutions have not capitulated to them. This is also because they are massively constrained by Ukraine's bid to present itself as a the bastion of "european liberalism": they don't have the freedom of movement and initiative to agitate for fascism because the Ukrainian state depends on us western liberal bleeding hearts for its survival and because its strategic objective is european integration, with which hegemonic overt fascism is incompatible. They are still be influential because of their war stripes (thanks Vlad...) but they have to "play by the rules" and play the game at the Meloni level, not the Kassidiaris level.

On the other hand, Russian fascists are operating in an explicitly ultranationalist, militaristic and illiberal space, with an openly and avowedly anti-liberal and traditionalist official ideology and doctrine. The putinist oligarchic regime depends on the depoliticization of the citizenry for its survival, actively suppresses every democratic right that russians ever had, and is deeply integrated with the schismatic Russian orthodox church, which is lead by a paranoid lunatic who blesses nuclear weapons and sacralizes the russian armed forces. Where Ukrainian fascists are politically constrained, Russian fascists are sometimes capable to set the agenda through the "military bloggers" sphere, and are so strong that at some point they even got to threaten the regime, as the Wagner melodrama showed (yes they lost, but if you think that after Prigozhin, the Wagner fascists have not been accommodated in the regime, I have a steel factory in Mariupol to sell you). But more generally, they are a very well functioning apparatus of a state that is ideologically extremely well aligned with them.

Where Ukrainian fascists are denied hegemony for the survival of the state, Russian fascists are coopted by the state and sometimes even threaten it. The political climate in Russia gives the fascists every boon and accommodation they might wish for. I can't think of a place where it would be easier to do fascist politics. Like, if there was a "let's play fascist ideological hegemony" video game, Russia would be the ...tutorial level, while Ukraine would be at least one level up from normal difficulty.

And, let's be honest: the fascists on both sides are much stronger today precisely because of Putin deciding to invade. If you're looking for "who carrries water for fascism", look to the Kremlin aqueduct...