Sacrificing the elves in the alienage and killing all the Dalish are probably the two worst things you can do.
Whether killing Connor is evil depends on how you get to that point. If you go into the fade and make a deal with the demon, that's evil. If you decide not to do the ritual and are "forced" to kill him, that is heart wrenching (because of the performance by Isolde's voice actress) but not evil.
Killing Wynne upon meeting her is something I could never do, even to reload and undo it. I could kill her after defiling the urn, but she brings that on herself. I can never just decide to wipe out the mages. Neither can I execute Alistair, although killing Loghain in front of Anora is pretty evil, too, and I do that almost every time.
I don't think abandoning Redcliffe is evil, just lazy. I never do it, but every time I play that level I wish I had.