My favorite 4 characters in general all happen to be villians: Both Weskers and both Baker parents. All these characters ooze personality, have depth, are distinct, are intimidating, and are otherwise just cool.
Lucas is close, and I love many more, from Irons to Carla to Birkin to Eveline. And of course the source of it all, Spencer.
My least favorite is easily Morpheus. Not only is his entire character revolving around a gimmick (and a silly one at that), but there is no explanation or further meaning to his ideals other than "he's crazy". He was really made the way he was so the devs could make a female Tyrant, yet why not use a female villian then? Or at least provide a solid backstory to justify his personality.
His plans are also stupid, and I find it hard to believe could convince anyone to follow him.
Just to clarify, 3A7 works for Blue Umbrella. Red Umbrella ended in 2003, then when Umbrella came back in 2007 they became Blue.
Red = classic pharmaceutical Umbrella with Spencer in charge (RE1-3, CV, TUC, etc)
Blue = new PMC Umbrella with new management. (UCorps, RE7)
The red version of the BU logo seen in UCorps is the symbol of BU's secret forces (essentially USS 2.0).