These affairs weren't all bad. Did the self combust of end in real love?
Carrie and Mr. Big -- Sex and the City
Carrie and Big on Sex and the City when she was with Aidan and he was married to Natasha in Season 3. The episode that comes to mind is "All or Nothing" when the first incident is shown through Carrie's guilt-ridden flashbacks. While I can't condone her actions, Big and Carrie were nothing if not passionate and most of us rooted for them despite our better judgement.
Alison and Noah -- The Affair
It's not called The Affair for nothing. How could we possibly justify any woman cheating on Joshua Jackson's Cole Lockhart? When the two leads so despicable that we want them together to give Cole and Noah's wife Helen a break. Yes, these two deserve each other for reasons other than the lust they share.
Annalise and Nate -- How to Get Away With Murder
These two are hot and heavy. Annalise is herself around Nate, but that's not all good. Her student catches them in the act and she doesn't apologize. Nate's later arrested for her husband's murder. Hey, the sex is good!
Ally and Billy -- Ally McBeal
The most scandalous affair that never was would be Ally McBeal and Billy Thomas. They attended Harvard Law School together, but he left to attend Michigan, breaking her heart. He was the one that got away and a kiss was as scandalous as an affair, ruining her relationship and throwing his marriage a curveball. Billy died in her arms of a brain tumor, envisioning the life he imagined he'd had with Ally.
Dwight and Angela -- The Office
Though Angela agreed to marry Andy, she couldn't help herself when it came to Dwight. News of their affair spread all over the office until everyone knew except poor Andy. Finally, Andy found out and challenged Dwight to a a duel which surprisingly ended with Angela losing both men.
Kara "Starbuck" Thrace and Lee "Apollo" Adama -- Battlestar Galactica
Kara 'Starbuck' Thrace was in a relationship with Anders when she had a one-night stand with fellow pilot (and also attached) Lee 'Apollo' Adama. Frightened by her feelings, she proposed marriage to Anders the next day and an injured Lee soon married Lieutenant Dualla. Later, after a sexually charged boxing match brought up their residual feelings, they started an ill-fated affair. While these friends and lovers could never quite get things right, there was no question that Starbuck and Apollo genuinely loved and respected one another.