i'm thinking up how hans would still be a villain if he goes after a direct heir , negating him having to kill anyone / 'use' his evil side.
in frozen , he only reveals himself because his plan is to kill elsa to be able to take the throne. had anna not been dying , he wouldn't have ever said anything &* most likely kept up his nice guy facade. would it have cracked eventually because he'd get tired of pretending ? maybe. it could certainly slip out in anger or annoyance , or his aromanticism finally catching up to him with boredom from his spouses lovesickness. maintaining the level of prince charming he was at is quite a stark difference from his real personality after all.
he could take after his dad ----- project the benevolent ruler to the people , work in the shadows to rule cruelly behind the scenes. use the same level of threat against his partner that his father used against his mother. he has quite the upper hand with his powers. threatening his spouse would eventually bring up his own childhood trauma of knowing how desperate his mother was to protect him from this exact future , so there's that arc. his mother was injured because of hans powers , but ultimately died because the king put no effort into healing her ------- punishment for keeping hans away from him when they could have already been training him with his powers. ( * yes , he's talking about training a toddler. )
i find it difficult to imagine him staying a villain if he has love is the issue i'm running into here.
lets say for instance that he married anna. if he did not immediately stage an incident for elsa &* simply let the 3 years run into frozen 2 , thus having anna become queen -------- &* negating my rewrite of him becoming good through being the fire spirit ------- when exactly would he reveal his evil side ? there is a high possibility here that he would be treated so kindly &* lovingly by anna &* her support system that he would never need to reveal his darker nature because he'd know what love feels like. essentially , he'd find himself not wanting to be that dark self at all. why would he throw away all this good for nothing ?
he is evil because of his environment -- everyone in the southern isles is out to manipulate &* lie , so he's never been able to trust anyone. anna wouldn't lie to him or hide anything -- she has no ulterior motive. it might take him time to trust that , but ultimately being in a safe place would nurture the part of him that is good.
the only real corrupting point i can reach for is power. regardless of love shown to him , his main canon point is power. he wants to be king --- he wants to rule over people , have full control of a kingdom , financial freedom , etc. that is his drive. at the worst , that means he wants to extort other kingdoms , expand his kingdom by force , have an army , things like that. given his skill is lying &* manipulation , i can't imagine this comes with an iron fist publicly. no one wants to follow you if you're very vocally evil.
the issue now is that love factor. so . . . ultimately , he probably plans on killing his spouse after they have an heir or two , assuming said spouse is not also a tyrant. if we assume that he is never swayed by love because he can't feel it , he'd keep his heart completely away from his spouse &* feel nothing for eliminating them. possibly remarry simply to have more heirs. this is easier to maintain in verses where we aren't actively writing a romantic ship. so if we were writing friends or rivals , it's easier to have the romance to the side instead of as a driving feature of the plot.
i think in disney fashion , love will always win out if we're writing a romantic ship. it is possible to write him as a through &* through villain who never redeems himself , but it's a stretch in the end. he is not immune to love &* the effects true love would have. the only real way to write him as irredeemable is to lean into the psychopathy side where he can't feel love or empathy. given his backstory , that isn't the case. he's learned those traits through watching others &* surviving within his family -- they are not innate to his biology ; he was not born with that mental imbalance the way his family is. ( * sidenote --- his brother lud is also not a psychopath / sociopath. there's something unwell about him , but not to the degree of the rest of them. the rest feel absolutely no remorse for their torture against hans. )
i want to say a strong enough friend could also pull him into being good , but that's a bit more of an easy one to side-step. unless they are in power &* he is in a position where overthrowing them might give him the throne , ( i.e. killing anna &* elsa was going to work for him because he'd be the savior of arrendale &* thus given the crown -- granted , he did lie about marrying anna secretly, but it is implied that the kingdom probably would have turned to him either way ) what does he have to gain from letting them influence him ? if he can overthrow them &* get their power , he will try -- here love can step in again ; will he ultimately betray someone who is showing him true platonic love ? iffier , but he may switch to good. if they are simply a friend that is begging him to not be evil , he has nothing to gain from them other than maintaining a friendship. he wants power -- if they are not powerful &* therefore elevating him to power at their side , they are in his way.
all in all -- a redemption arc is pretty much always canon with anyone romancing him unless he truly truly dislikes them. even then , he has never known love , so anyone showing him genuine interest &* affection will probably win him over in the long run. while he may not expose a truly evil side unprovoked , he would eventually relax to show his more honest personality -- witty , sarcastic , more n s f w , brooding , etc. he would admit his prince charming act is dishonest , but he'd never go fully detached &* cruel without prompting. he'd have no reason to. i think he will always unlock the part of him he suppressed as a child --- the softer side that didn't want to hurt anyone &* believed in good.