Dukat was definitely more developed but I think in terms of notoriety Khan beats him hands down. People who aren't necessarily Trek fans are more likely to know Khan, if only through "that" moment when he strands Kirk on what would be the genesis planet.
"I'm leaving you Sisko, like you left me"
"Dukat"
"DUUUUUUUUUUUUUUUKKKKKKKKKKKKKKKKKKKKKKKKAAAAAAAAAAAAAATTTTTTTTTTTTTTTTTTTTTTTT
^
