Master Chen's powers and abilities
Before his banishment from Ninjago, Chen was an intellectually self-serving man who was able to manipulate both Garmadon to crave power, and the Elemental Master of Earth (in addition to others unmentioned) to fight against the Elemental Alliance. This manipulation served him in keeping a balanced rift between the Elemental Alliance and the Serpentine in the Serpentine War. At this time, he also proved to be a master strategist, twisting moves on both sides in such a way to keep his involvement in the dark—an aspect that grew stronger in the years to come, with the newer generation of Elemental Masters.
After his banishment, however, Chen became more childish, spoiled, and impatient (all of which he expressed while supervising the Tournament of Elements), but still devious and greedy. He also has a quirk, which is his love for buttons and trap doors (which is a combination of his need for power and childish nature). During the Second Serpentine war, Chen started to complain how difficult and time consuming it was to take over Ninjago.
However it would appear that Chen did love his daughter, and gave her special treatment (he provided her with a tournament suit similar to those of the Ninja, and he allowed her to keep Kai around after he had drained him of his power). After she betrayed him, though, he no longer cared for her safety, and his greed took over.
He is also shown to be culturally insensitive, as he used the symbolism of the Anacondrai, even after betraying both human and serpentine by igniting the war that drove both sides to near extinction. He even violated their remains by using them as decorations and clothing, while espousing their ideology of "only one can remain," adding insult to injury. He is also shameless in this, as he begged the spirits of the Anacondrai generals to spare him even though he was the one who instigated both wars, which caused them to be banished to the cursed realm, and then used elemental power to transform himself into a pseudo-Anacondrai while claiming to be on the same side.
Chen is also shown to be temperamental, sadistic, and possibly psychotic. This is shown in his previously mentioned duplicity, hot temper, and tendency to believe his own lies. He also showed great enjoyment and schadenfreude when he revealed to Wu and Misako that Garmadon had signed the love letter that Wu had written for Misako that caused her to fall for Garmadon in their youth. Chen's perverse glee is quite evident in this action, and only further showcases his psychosis.
Chen is also shown to be quite cowardly, and is seemingly incapable of owning up to his own mistakes and misdeeds, claiming that his use of magic to become an Anacondrai meant that he was on their side in a futile attempt to be spared by the unleashed spirits of Arcturus and his comrades.