Quad Smack

Quad Smack is the Antitrix equivalent of Four Arms. He is voiced by Greg Cipes and first appeared in the season 3 episode Which Watch. 

Quad Smack in The Bentathlon

Appearance

Quad Smack shares the general shape of Four Arms, except he's purple instead of red. He wears a black and red sleeveless jumpsuit and has grey metal armor on his shoulders. He has a beard-like mark on his chin as well as red eyes. He wears black gloves with red fingertips and three silver spikes on each glove, as well as black markings on each arm. He wears the Antitrix symbol on his chest.

Skunkmoth

Skunkmoth is the Antitrix equivalent to Stinkfly. He first appeared in Introducing Kevin 11 and is voiced by Greg Cipes.

Skunkmoth in Introducing Kevin 11

Appearance

Skunkmoth is a beetle-like humanoid with a muscular build about the size of Four Arms. He has red skin and wears golden armor on his shoulders, knee pads and legs. He has two golden plates that usually cover his large red wings. He has three spikes under his large jar and has a grey horn that curves upwards. He has red eyes and wears the Antitrix on his chest. 

Dark Matter

Dark Matter is the Antitrix equivalent of Grey Matter. He is voiced by Greg Cipes and first appeared in the season 3 episode King of the Castle.

Dark Matter in You Remind Me of Someone

Appearance

Dark Matter is a very tall and lanky red frog-like humanoid with a large head. He has four long red fingers with claws and wears black pants. He has two front toes and one toe on the back of each foot. He has two round, red glowing eyes with minus-like pupils and wears a grey vest with two lines on each side, which are presumably his gills. He wears the Antitrix symbol on his chest.   

Crystalfist

Crystalfist is the Antitrix equivalent of Diamondhead. He is voiced by Greg Cipes and first appeared in the season 3 episode Franken-Fight.

Crystalfist in Franken-Fight

Appearance

Crystalfist is a well-built humanoid composed of purple crystals. He wears a black uniform that covers his torso and legs with a jagged purple V on the upper torso. He has rib-like crystals potruding on his waist as well as his knees. He has two crystal shards on his back, four fingers shaped like claws and has a sharp spike on his bulky shoulders. He sports a different shaped "helmet" on his head. He has red eyes and white soles. The Antitrix symbol is on his chest.  

Undertow

Undertow is the Antitrix equivalent of Overflow. He's voiced by Greg Cipes and first appeared in King of the Castle.

Undertow in You Remind Me of Someone

Appearance

Undertow is a circular blue metallic alien. He has round has tubes connected from his elbows to his head as well as pipes on his arms and stomach. He also has two tubes that connects from his respirator to his chest. He has four black fingers on his arm tanks as well as three black toes. He has a black mask-like marking as well as red eyes. Murky green water can be seen inside his canisters. He has a black protrusion on the top of his head with three red buttons. The Antitrix symbol is on his chest.