Well, he only has two kids, and one is from an alternate future where he got killed off so doesn't count.
The answer here is Cable.
Cyclops was willing to give up his only (legitimate) son to a time traveler from the future, knowing (at the time) he would never see him again because it was the only way to save him- putting his personal feelings aside for what was good for the kid.
Ok. "so what" you say. That's selfless, but not being a good Dad. Cable would agree, coming back from the future to tell Cyclops what a worthless piece of crap he was, leaving him to grow up in a hellish future where apocalypse rules everything.
And cable had a point.
UNTIL we find out that after the cyclops and jean grey wedding, Rachel Grey pulls Scott and Jean thousands of years into the future to save a young nate grey and raise him.
Scott and Jean spent about 15 years (give or take) in the year 3000 with busted powers and a broken leg (Rachel didn't have enough energy to bring them there at full strength, and scott was injured in an early attack) not only raising cable in apocalypse's future into someone morally and physically strong enough to overthrow him, but also caring for a geriatric rachel grey that had put herself into a coma using up the last of her powers.
You can say a lot about Cyclops, but "bad father" isn't one of them.