He is one of Thanos' second in command, and a general to Thanos' armies. He has superhuman strength, superhuman speed, invulnerability, he is an expert at hand to hand combat, he is a master strategist, and he only die if the blade of his scythe is broken.
Corvus Glaive first appeared in the Season 2 two-part episode "New Frontiers", as a member of the Black Order. He and the other members infiltrate a special prison, where they end up taking out its defences, and free their master Thanos. When the Korbinite Jeter Kan Too of New Korbin begs the Avengers to save them from mysterious invaders, the team discovers that Thanos and his Black Order are plundering New Korbin.
His second appearance was in the other half of the episode "Avengers World", in which the Black Order attack Earth, finally planning to take over the planet by destroying the Avengers.