I kinda wanna call river. Feels like a lot of missed draws in villain's range and I'm not sure what value hands make sense. 44 is the only thing that makes sense to me.
It's a strange one but I think you have to call. The 9 is kind of a brick here and doesn't change too much in terms of hand strength between the two of you. He's either rivered a monster with 44 or he's choosing to slowplay something huge like TT,99. Go for a call.
This strange river donk by villain actually looks like a hero call because if he has Tx he'll probably use it as a bluff catcher rather than value bet thinly.
If he has a 9x he should raise turn and kill your odds in case you are delay cbet semibluffing.
On the other hand he could have quads or the nut FH and was hoping you hit your sd or fd to get you to call a large river bet , because your Tx would probably bet the flop. And so makes a 3/4 psb on blank river to make up for value he should've gotten for raising turn. Also a rivered 44 makes sense for him as well.
I think villain is unbalanced here and has more bluffs than he should.