This isn't actually the form which will decide what is worse.
On one side, she was clearly suffering in her couple, after having done everything possible to keep it together. Can we really blame her to drift apart and finally have feelings for someone else ? Sure it was before they get separated, but it was only a premice, and well deserved for him.
On the other side, he clearly did nothing for their couple, just seeing his wife as a convenient tool. And refused having sex with her for 2 years, pretending he hates sex... to have sex with a coworker at the 1st opportunity. The guy is clearly trash, no excuse. He finally realizes, it, but that's way too late, he totally deserved what happened to him, while she really did her best.
