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

Crystal Snailigma

Source: Crystal Snail
Mega Man X2 (SNES) by Capcom

Magna Cigmapede

Source: Magna Centipede
Mega Man X2 (SNES) by Capcom

Overdrive Ostrigma

Source: Overdrive Ostrich
Mega Man X2 (SNES) by Capcom

Wire Sigmonge

Source: Wire Sponge
Mega Man X2 (SNES) by Capcom

Sigmarnov

Source: Karnov
Bad Dudes Vs. DragonNinja (Arcade) by Data East

Sigmarch Viligma

Source: Arch Vile
Doom II (PC) by id Software

Sigmalien Queen

Source: Alien Queen
Alien vs. Predator (Arcade) by Capcom

Nessigma

Source: Ness
Earthbound (SNES) by Ape and HAL Laboratory

Sigma body from custom sprites by @hansungkee1

Sigmad Spencigma

Source: Rad Spencer
Bionic Commando (NES) by Capcom

Earthworm Sigma

Source: Earthworm Jim
Earthworm Jim (SNES) by Shiny Entertainment