He is an evil wizard who experiences physical pain by love and care, he seeks to destroy all the feelings in the world - possibly due to the fact that it pains him or, more likely, simply because he wants to.
The majority of No-Heart's power derives from a magic amulet, a trait that he shares with Dark Heart - the chief antagonist of the movie Care Bears, A New Generation.
As well as his stated goal of obliterating love and care from the world he is also a classical Dark Lord and dictator who dreams of taking over the world - employing such means as his shadow servants - who steal feelings from "good" children and make them develop bad traits such as selfishness and greed.
His main henchmen is Beastly, a largely comic-relief minion with a very high failure rate - like many Dark Lords No Heart often abuses Beastly, usually as punishment for his failings.
Later in the series No Heart's niece Shreeky decides to help in the fight against the Care Bears, a development No Heart found great displeasure with.
No Heart rarely allies with other villains - a noticeable exception to this was a very brief team-up with Dr. Fright, in general though No Heart is a solo villain who doesn't get along very well with his own minions - let alone any other villain.
No Heart is also notable as one of the more dark and serious (at least in mannerism) of the Care Bears villains - he is probably one of the few, if not only, villain the Care Bears have encountered who is almost pure evil in every aspect.
No Heart shares some certain similarities with Teddy Ruxpin's Quellor.