Stitch is one of two titular main protagonists of Lilo & Stitch franchise.
History (just about Villainous Acts)
Lilo & Stitch
He was designed to be evil. Jumba Jookiba said that Stitch needs to destroy towns, and was happy when he heard that Stitch crashed on Earth, and that he will try to use his destructive powers on Earthlings.
He stole police spaceship to escape from galactic federation who wanted to destroy him because of his evilness.
He laughed evilly several times.
He attemped to kill frog with space gun.
He frightened dogs to their death.
He caused rampage and destruction in Lilo's house.
He sadistically tormented and frightened people who were photographing him.
He threw book on Cobra Bubbles and hit his head.
Stitch Has A Glitch
In his dream, he destroyed everything on his way (even hurt his lovely Lilo).
He made rampage and destruction in Lilo's house.
He made rampage and destruction in Hula School, he viciously attacked hula girls and their teacher (maybe tried to kill them) and destroyed whole school.
Lilo and Stitch: The Series
In episode 627, he was supercilious, because he thought he's special and no one can beat him. During the dinner, he thought that he needs special treatment, because he is special. He threw salad out of dish on the floor, and put it on his head When Pleakley said that they will never give him anything if he don't say "please", Stitch threw dish full of mashed potatoes on his head. When Jumba told that Stitch started to act like blue peacock, he gonna mad and threw plate with beet in his head. That maed Jumba mad and caused him to make experiment 627, who is much stronger and more dangerous than Stitch. Later, Stitch became sad because he understood he isn't that special at all, but Lilo and him found out how to defeat 627.