Okay, so we have:
-Concept Art Robotnik
-Original Dr. Robotnik
-AoStH's R-R-R-ROBOTNIK
-Sonic SatAM/Sonic Underground Dr. Robotnik
-Dr. Eggman (Dreamcast Era Robotnik)
-Sonic 06 Dr. Eggman
-Eggman Nega
-Julian Kintobor (Secret Rings' Alternate Universe Eggman)
…And, last but not least…
-Modern Dr. Eggman (Sonic Boom's Robotnik)

Especially with the voice of Jim Cummings. That guy's got great range, he can do creepy and/or intimidating voices like SatAM Robotnik and the death mask from the Splatterhouse reboot, but he can also do some of the most innocent sounding characters ever like Winnie the Pooh and Tigger.