It's too bad they can't fly and that BB has one of the highest plot hypes. It hurts to admit but I think Blackbeard could actually win
His black hole is the key to winning against most characters. When he fought Ace he could have won the first minute but he wanted to try
Ace first. He sucked in the whole town where they were and spared Ace just so he could behold his power xd He's basically an ass and his only weakness is
his arrogance but when against 3 swordsmen like this I don't think he would be that careless. It sucks to face Blackbeard in combat. Someone really fast, with good ranged attacks and with good geppo or other means of flight would
be the best matchup against him, so I'd say if you switched Mihawk for Doflamingo it would be much easier to win because it's also possible that Doflamingo could help Zoro and Law by grabbing them and throwing them in the air

I'd say Marco is a very good opponent for Blackbeard aswell if he plays his cards right and is able to outperform him in melee. Well there's also the obvious Kizaru. That could be a tough fight for BB lol