Gigantic spoilers for Radiant Historia Perfect Chronology (watch out if you only beat the original because of the added story content)
I can only empathize with Heiss's motives throughout the game.
Basically the world is slowly dying because the Ole Empire fucked up big because of the emperor's cruelty, and now there's a big mana-eating monster that cause the world to slowly become a desert.
There's one way to slowing down the desertification and it is for the Royal Family of the actual new kingdom to make a sacrifice : one of the royal children has to sacrifice their brother/sister for it.
Heiss was the late king's brother destined to be sacrificed, he noped the fuck out of it, killed his brother and took his nephew (who was also a potential sacrifice) with him.
Heiss basically wants to destroy the world that wants him and his nephew (the main protagonist) dead. He's angry at the system that allows for others to live on the sacrifice for others and you can't fault him for this.
Granted, Heiss isn't all white : he still killed his brother (that wasn't necessary), the whole group of mercenaries Raynie and Marco were in just because he wanted some pawn/fodder for Stocke, tried to kill Eruca. But the "true" ending has him sacrificing himself to spare Stocked, and he completely follows the heroes when presented with a solution that allows for the desertification to completely stop without having to sacrifice anyone in the "true true" ending.
So yeah he's imho the best villain of JRPG since a while ago
Basically the world is slowly dying because the Ole Empire fucked up big because of the emperor's cruelty, and now there's a big mana-eating monster that cause the world to slowly become a desert.
There's one way to slowing down the desertification and it is for the Royal Family of the actual new kingdom to make a sacrifice : one of the royal children has to sacrifice their brother/sister for it.
Heiss was the late king's brother destined to be sacrificed, he noped the fuck out of it, killed his brother and took his nephew (who was also a potential sacrifice) with him.
Heiss basically wants to destroy the world that wants him and his nephew (the main protagonist) dead. He's angry at the system that allows for others to live on the sacrifice for others and you can't fault him for this.
Granted, Heiss isn't all white : he still killed his brother (that wasn't necessary), the whole group of mercenaries Raynie and Marco were in just because he wanted some pawn/fodder for Stocke, tried to kill Eruca. But the "true" ending has him sacrificing himself to spare Stocked, and he completely follows the heroes when presented with a solution that allows for the desertification to completely stop without having to sacrifice anyone in the "true true" ending.
So yeah he's imho the best villain of JRPG since a while ago