Aang!!!!!!!!!!
Nine-Tail Fox Spirit won't do dick against the Avatar State. We're talking wild uncontrollable power against the wisdom and power of every Avatar prior to Aang. It's power and experience VS just power. And if Naruto decides to go all transgender, Aang can easily overcome his lustful desires. He is a monk after all.
Alucard. Despite having some of the worst lines in anime (Go to bad place and lick the Devil's ash!! WTF!!!??), Alucard is a force of nature that can't be overwhelmed. He could take all of London with him if he wanted to. Dante is a little to cocky for his own good, willing to take hits and stabs just because he thinks he can get up from them. Maybe a few melon sized bullet holes will change his opinion on dodging. The moment these two go Demon, Alucard still has the upper hand since his demon form seems incorpreal or intangible while Dante still has a physical form. Almost seems like a no contest. Well, Dante had it coming, the punk