Civilization 6 is a game I very much enjoyed, but most players agree the warmonger penalty was too harsh.
Civ 6 would end up hitting players with punishing warmonger penalties seemingly whether they were playing aggressively or not. You could end up getting punished even if you were defending yourself from the already aggressive civ AI.
As part of the Spring 2017 update for Civilization 6, out this week, the developers at Firaxis have added nuances to the warmonger penalties so they only hit with their full strength if you are "truly wresting valuable cities from your opponents".
Let's dig into the detail. The update adjusts warmonger penalties for Diplomatic status. So, when applying a warmonger diplomacy penalty for either declaring war or capturing a city, the game will now reduce that penalty if you are enemies with the target of that warmongering.
Here's an example, provided by Firaxis:
Similarly, the update adjusts warmonger penalties for City Population. So, when applying a warmonger diplomatic penalty for capturing a city, that penalty is reduced if the city is smaller than the average city in the game.
Here's another example supplied by Firaxis:
Elsewhere, there are a number of balance changes, AI adjustments, multiplayer changes and bug fixes. The patch notes in full are over at the Civilization 6 Steam page.