In Twilight Princess, there's that boss in Snowpeak I always thought was really odd. It's a small woman who becomes this possessed, giant, ice ornament thing and she tries to crush you. It's not physically weird looking, but you're in her home, fighting her, it was kind of a plot twist. Another boss I can think of that's weird to me is "God" in Silent hill 3. Silent Hill is pretty convoluted, so I don't understand why it's called God or why it looks the way it does, I guess most/all boss fights in the Silent Hill series could be considered weird. And Lastly, the curse-rotten greatwood in Dark Souls 3 is weird, just by the way it looks.