Beleth is a decently strong fighter who certainly knows what it is like to be on the winning side of a fight. Still, he will have a tough time getting past Sasuke of the Uchiha clan. Sasuke has visual jutsu that are leagues ahead of any other and his teleportation will allow him to get the drop on Beleth whenever he pleases. As such, Beleth has no real way of landing a hit. Sasuke wins.