The resolution, which began last week with Chuck's breaking into Wendy's laptop to see her notes about Axe - though perhaps not really breaking in, if we buy Chuck's argument that how can you be breaking in if the owner of the laptop has given you the password? - came to a head in the only way possible that didn't strain belief: Wendy leaves both Chuck and Axe.
She has ample reason and motive to leave both - the two bitter adversaries have been using her mercilessly throughout the show. That she put up with this so long, that Chuck and Axe each put up with it for their own different reasons, was unbelievable. But Chuck loved her, as did Axe in a way, and this along with each using Wendy as a barometer of what was going on with the enemy is what kept this intense and bizarre triangle in motion, kept us distracted and even mesmerized enough to let it keep ringing.
I've got to say - and Bernie Sanders wouldn't like this (but who cares) - that I think Axe has at least the slightly superior argument in that great one-on-one between the two at the very end of the episode. Yeah, Chuck may be a right in a narrow technical, legal, sense, but Axe has the superior moral position when he points out whom is he really hurting in his wheeling and dealing, which certainly benefits lots of people. Both men have done wrong to their personnel, but as far as the world at large: which one has really brought more value to the world?
It's also clear that part of Chuck's rage against Axe is not just about what Axe may be doing that's illegal, but about what Axe may be doing to Wendy. We the audience know that they haven't slept together, but even if Chuck could be sure of that, he would still deeply resent the emotional connection between Axe and Wendy. His use of his office to prosecute that is surely an abuse of power.
Chuck's anger over Wendy won't be abated by her leaving Axe, because Wendy has also left Chuck, who not completely incorrectly blames Axe for Wendy's leaving Chuck, even though Chuck knows he is to blame for this too. It will be fun to see what new role Wendy plays in the next season, and for that matter, fun to see the next season in general, at which time we'll have a brand new President, too.
See also Billions on Showtime: Winning Me Over ... Billions 1.6: Pivotal Wendy