Spoilers (for context) below:
As far as historically "toxic" MLs go, he's rather tame. His red flags are preshaded by his supernatural nature; he’s not entirely human, a Tiger God(?), so he’s slippery around human conventions. That said, he has a healthy relationship with his sister and mom, which shows he’s human enough to foster and nurture deep connections.
He’s already disgustingly devoted (he fell first, and fast) to the MC, even if he hasn’t realized it yet. So no, I wouldn’t call his flag red, just spooky.
Aside from their post-wedding dubcon union, the ML doesn’t hurt the MC in the way you might expect. He IS pushy about sex, mostly to tease the MC and prove a point, but by that stage, the MC has already fallen in love with him. His worst offense is probably his extremely dirty mouth and mind, especially since the MC is about as virginal as they come. In a way, they’re also cute and couple-y but they’re both oblivious to their own feelings. It’s embarrassing.

Is the ml toxic red flag...? I hate those bro... especially in the historical setting ....I started this thinking they'd be cute and couple-y but we're off to a weird start...