Sigma Posting (Follow on BS)さんのイラストまとめ

Sigmeldia

Source: Zeldia
Guardians (Arcade) by Winkysoft

Bligma

Source: Black
Final Fight 3 (SNES) by Capcom

Bratigma

Source: Bratken
Final Fight 2 (SNES) by Capcom

Sigmazuki

Source: Mizuki
The Punisher (Arcade) by Capcom

Sigmocide

Source: Scumocide
Captain Commando (Arcade) by Capcom

Sigmutcher

Source: Butcher
Cadillacs & Dinosaurs (Arcade) by Capcom

Steampunk Sigma

Source: Stage 4 Boss
64th Street: A Detective Story (Arcade) by C. P. Brain

Maveroshi Yuukigma Sigmori

Source: Maboroshi Yuuki Yamori
The Ninja Warriors (SNES) by Natsume

Sigmonty Burns

Source: Monty Burns
The Simpsons (Arcade) by Konami

Maverick Trevigma, Maverick Sygma, & Maverick Sigmrant

Source: Fake Trevor, Fake Sypha, & Fake Grant
Castlevania: Symphony of the Night (PS1) by Konami

Sigma heads edited from sprites by @hansungkee1 and Aburtos