yes, harry himself used the cruciatus and imperius curses several times.
- I don't think I'd call it "several times." He used the Imperius Curse once, in a Gringott's Goblin, and the Cruciatus Curse once, weakly, on Amycus Carrow. 17:08, January 6, 2019 (UTC)
Also, McGonagall uses the Imperius Curse on Amycus, and Snape (if you can call him a good guy) uses the Killing Curse on Dumbledore.
In the movie, Ron uses the Killing Curse to ty and kill Nagini just before Neville beheads the final horcrux.
Harry used the Cruciatus Curse on Alecto Carrow and tried using it on Bellatrix but it wasnt at its best because of its true heart.