Men in Black: The Series (1997)

S1E4 The Alpha Syndrome

While looking into the heist of a Sintillian heart, Kay uncovers that the mastermind behind it is Alpha, his old mentor who betrayed him and left him for dead years ago. As Kay and Jay dig deeper, they find that Alpha has undergone drastic modifications, with various body parts fused to him, making him an even greater threat than before.