Kylo Ren is basically just an emo kid with fits of rage.
This is especially true for Episode VII, in Episode VIII he grows up a little towards the end, and is more calculate, cold and deliberate. But up to a point where Snoke criticized him, he was really immature, venting his frustrations on equipment and/or people around him with no good rational reason.
Note that emotional outbursts are sign of weakness for Dark Side users, although they use hate and rage to fuel their powers. But they should control their emotions, not be controlled by them . For example, Palpatine almost never got carried away by his feelings, and once he did (torturing Luke) he was killed. Same could be said for Snoke. Vader himself, idolized by Kylo, had some outbursts at beginning of his career, and that cost him arm and a leg (literally :) ) . Later, he was completely cold even when he punished his subordinates. Maul, formerly Darth, lost a fight and his life when he allowed Kenobi to anger him ("And what do you have ?") .
Note one more thing about Kylo, he was mimicking Darth Vader with his helmet. Unlike Vader, he has no real purpose for it, and other Dark Side users did not hide their faces without reason. His helmet was instead symbol of him not accepting himself, another sign of immaturity. Once he got rid of it things stared to progress for him.