The Sigma Force also known as the M2 Commandos, and the Mega Cannon Sigma (メガキャノンΣ Mega Kyanon Shiguma) are General Rilldo's top mercenary force. It is made up of four Machine Mutants: Commander Nezi, Bizu, Ribet, and Natt. The commander of the Sigma Force is Nezi.
The Sigma Force are first encountered by Trunks, Goku, and Pan on planet M-2 when they attack the group, taking Goku and Trunks. When General Rilldo realizes Pan is in the base, he sends Natt to deal with her. The robot seems to be winning with ease, but then Pan figures out he can only predict moves she has done before. She combines some of her moves with Goku's, and then destroys the robot. Later, when they battle with Goku, the Sigma Force (with the exception of Natt) fuse together to create one mighty robot, the Super Mega Cannon Sigma.
- The Sigma Force bear similarities to the Ginyu Force, such as dramatic posing and the confidence in their abilities to defeat any opponents who stand in their way.
- In Super Dragon Ball Heroes: World Mission, Super Mega Cannon Sigma is named Super Σ, as Σ (or Sigma) is the 18th letter in the Greek Alphabet. Similarly, Sigma Force can also be spelled as Σ Force.