I can't do very well fighting him. I can't figure out a good strategy to fight him. I'd appreciate some advice.

it depends the character you choose, almost on all cases, the final boss is NU-13 (Middle / close). try to use each characters in the correct way. and understand its operation for example if you want very fast combos, Iron tager is the worst option ....

Iron tager - close
Hakumen - close
Ragna - close
Taokaka - Middle / close
Bang - Middle / close
Noel - Middle / close
Nu13 - Middle / close
Rachel - Middle / Far
Laichi - Middle / Far
Jin - Middle / Far
Carl - Middle / Far

Remember this not applied exactly as I told you, because all the characters have some special attacks, as in the case of rachel is advisable to keep the distance and attack close at the right time. try to memorize the combos you make and cause greater damage.

regards

Noel, Laichi, and now Taokaka are my favorite characters.

I haven't tried any other characters yet.