Hannibal has feats against Jack Crawford now (a VERY impressive fight scene). Jack does have tactical and military training, and while he is older he is very strong and showed considerable skill, both of them. Hannibal also showed the ability to slow his heart rate down and feint fainting/passing-out, freakin' brilliant.
Hannibal has Ju-Jitsu and/or Judo training, as well as Kendo and possibly Karate. He would, too. He showed trained-knowledge in striking, grappling, knife-handling, and at this point he's had more fight scenes than Dexter has all eight of his seasons. Which is sad, Dexter's best fight scene was Doakes and an imaginary one as "The Dark Defender."
Hannibal also killed....4-5 FBI agents, took down a highly trained FBI agent in Beverly whom is extremely proficient with her sidearm (she and another agent are like pre-Clarice Starling-types. Will Graham is probably the closest thing in the Hannibal world to his level of intellect, not even Clarice comes close. I think Dexter would come damn close to Will Graham, and obviously not be bothered by it)
Ironically I think if anything Hannibal would likely take Dexter down but not kill him. I think he'd do exactly what Dexter tried, what, three times? (Succesfully once, and she left, Lumen) and partner-up with Hannibal. Dexter has the same proclivities for waxing-poetic (though more inside his head), he has the same obsession over embracing his darkness and figuring out humanity.
Though Will Graham would run circles with him in the empathy-yet-still-psychotic-and-thus-able-to-understand-them department. At least until Hannibal shifted Dexter's thinking.
The biggest problem is that eventually Dexter would HAVE to fight Hannibal because one must control the other, and Hannibal can NOT be controlled. Dexter can, usually not for long and (so far) he has come out on top.
If I had to put this into comic book terms it'd be like this:
Hannibal=Deathstroke/Slade Wilson, an Apex human whos intelligence cannot be matched by any, only Lex Luthor, Bruce Wayne, and Ras Al Ghul even remotely come close. This is the guy out out-batmans the Batman
Dexter-at-his-best=Nightwing, a fantastic superhero and sometime-opponent of deathstroke himself. Batman thinks one day Nightwing might surpass him in martial powress but probably not in detective/criminal profiling, that goes to Tim Drake (Red Robin), meanwhile his son Damien seems to have it all but I digress.
Dexter is close-but-no-cigar at his very best. Hannibal was there 10-steps-ago.
He's pulling all the strengths, and just like when Nightwing beats Deathstroke, it's the hubris of the superior man that brings him down. The wings of almighty Icarus melting before the brilliant heat of their madness.