Richardson has usually portrayed villainous characters due to his deep and powerful voice.
His credits include Captain Gantu from Stitch! The Movie, Shnitzel from Chowder (the first episode; later replaced by John DiMaggio), Goro in Mortal Kombat, the second voice of Skulker on Danny Phantom, Sarevok in the Baldur's Gate series, Jolee Bindo in Star Wars: Knights of the Old Republic, Crunch Bandicoot in the Crash Bandicoot games, Tartarus from Halo 2, Ultimate Supreme Executive Chairman Drek in Ratchet & Clank, Antauri in Super Robot Monkey Team Hyperforce Go!, Openly Gator from Queer Duck, Doctor Payne and other characters on The Proud Family, Darth Laser (an obvious parody of Darth Vader) on Fairly Oddparents, Maurice the Aye-Aye from The Penguins of Madagascar, and the voice of Exile in the late 1990s cartoon Road Rovers. Richardson replaced Keith David as the voice of Tombstone on The Spectacular Spider-Man. In 2001, he voiced Barney Rubble on the TV animated movie The Flintstones: On the Rocks, his version of Barney Rubble's voice was more similar to the early Mel Blanc voice than to the Ed Norton imitation, which Blanc later used on the original Flintstones.