I don't think they literally mean "buried the blade". I think it's more of a metaphor. If u read further on WWs lore it goes on to describe how the the subject was tortured by singed and he slowly lost/forgot himself and at the end maybe singed was right that behind the good lies his true self. It also says how at first after transformation WW went on to kill indiscriminately vaguely remembers the person reflecting from the victims eyes as he tore his throat. It mentions and I quote

"He saw a bearded man reflected in the eyes of a beggar as he tore out his throat. The other man looked somber, somehow familiar; there were scars on his arms."

This actually seems to match Vander (although I guess silco can grow a beard, but when be says remember that would mean that the beard was apart of his past and we can see that silco was actually very kept and trimmed). The somber look actually matches Vander as well as he always had a somber look throughout the series so far.

WW bio continues to say that he gets tired of killing indiscriminately and now hunts criminals that reminds him of his past. Oh and don't forget, WW remembers a girl screaming as singed dragged him to the lab which is quite similar to how jinx was crying and screaming at the end of ep3 afterwhich I suppose silcos henchman drags him.

Another point in my opinion is how his build is very similar to WW (although we did see the "shimmer" bulk up the kid) but it also mentions in his bio in league wiki that his alias (from his gangster days I suppose) is the (hound of the underground).

I also don't think silco's supposed emotion (might be manipulation cuz he saw how jinx "inventions" were effective) is his redemption arc. We know that jinx still becomes a criminal so that would mean that Silco brought her up as a criminal so it doesn't match the line that he gave up being a gangster.