Sforno on Numbers 22:6/ספורנו על במדבר כ״ב:ו׳

1אולי אוכל, after you have cursed them.

2נכה בו, I militarily and you by means of curses.

3אשר תברך מבורך, actually Bileam’s power did not consist in blessing but in cursing people by mentioning their failings at a critical moment in G’d’s timetable, as elaborated on by our sages in B’rachot 7. This is why Balak did not demand a blessing from Bileam to make him victorious in war, or at least to be blessed so that he could fight the Israelites to a standstill. But when he nonetheless added the words ידעתי את אשר תברך מבורך, he did so only as a way of flattering Bileam.