Widmore wanted Ben to kill Danielle, and when Ben returned with the baby, Widmore told him he should have left it to die if I remember correctly...which apparently I do not...
S05E12 Dead is Dead Transcript
http://lostpedia.wikia.com/wiki/Dead_Is_Dead_transcriptWIDMORE: Well? Did you do it?
BEN: We had a...
BEN: ...complication.
BEN: I'm sorry.
WIDMORE: Is that a... baby? Your orders were to exterminate that woman.
BEN: Why? She's no threat to us. She's insane, Charles. Besides, you didn't tell me she had a child. What was it I was supposed to do?
CHARLES: Kill it.
BEN: It's not an "it". This is a child.
WIDMORE: You might find this difficult to understand, Benjamin... every decision I've made has been about protecting this Island.
BEN: Is killing this baby what Jacob wants?
BEN: Then here she is.
BEN: You do it.
But, as it is up there, when Ben presents Alex for Widmore to kill, he can't do it. So I don't think that makes him that evil, because if he really wanted to do it, then he would have.