I know people hate the show, but Galient has some boss designs.
I've never seen anyone "hate" the show. It's just average, not unlike other shows of that time like Orguss - just because it isn't a 10/10 masterpiece doesn't mean it's automatically shit.
inb4 "all of them"
But really, what constitutes fantasy mecha? Swords and capes?
I dunno, I'd say the setting more than anything else. I guess mecha in a series where most people fight with swords and capes would be called fantasy. A mecha with a sword and cape in a setting where people shoot each other with laser guns would still be considered scifi.
While its fantasy status is held in contention by some parts, I liked Break Blade's golems. Hykelion is basically Darth Vader as a mech and it's great.
Goddamnit I was going to post that.