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

Frog Sigma

Source: Frog King
Chrono Trigger (SNES) by Square

Monosigma

Source: Monokuma
Danganronpa by Spike Chunsoft

A guest edit by @GanbareLucifer

Sigmulgore

Source: Fulgore
Killer Instinct (SNES) by Rare

Sigmue

Source: Nue
Breath of Fire III (Playstation) by Capcom

Ruby Sigma

Source: Ruby Weapon
Final Fantasy VII
Final Fantasy Record Keeper (Mobile) by DeNa

Sigmack

Source: Jack
Streets of Rage 2 (Genesis) by Sega, Ancient, MNM Software, Shout! Designworks and H.I.C.

Nightsigma King

Source: Nightmare King
Little Nemo: The Dream Master (NES) by Capcom

Sigmero

Source: Zero?
Mega Man X2 (SNES) by Capcom

Sigmagile

Souce: Agile
Mega Man X2 (SNES) by Capcom

Sigmerges

Source: Serges
Mega Man X2 (SNES) by Capcom