There's probably a lot more than this but the two that came to mind instantly were Destiny 2 and Anthem.
Destiny 2: I expected them to follow the pattern they had set with Destiny 1 of annual expansions with Eververse lurking in the background. I had given them the benefit of the doubt with regards to Eververse and it did, in fact, seem like they were living up to what they had said Eververse was going to be for: Seasonal smaller content like the holiday events and things like Sparrow Racing League. Then the sequel came out and Eververse greatly expanded. Then they split from Activision and everyone thought it would get better but it got worse. Now we have yearly expansions, FOMO-bait paywalled seasons, vaulted content, paywalled dungeons, and Eververse.
I burned out midway through Shadowkeep, only came back for Beyond Light because it was on Game Pass, then quit again. Every time I consider coming back I remind myself that they put the 30th Anniversary dungeon and other dungeons behind paywalls and it reminds me to stick to my "Fuck Bungie" mantra. I regret ever giving them a penny in Eververse MTX, or buying Forsaken or Shadowkeep.
Anthem: Well this is self explanatory really. I hoped for the best, got a steaming pile of shit instead. Stupidly had ordered the Legion of Dawn edition which was available for $9.99 about six months later. At least I never spent a penny in their god awful store.
Edit: Y'know, the more I think about it, most of the games I regret buying or spending any money in/on were all from last gen. I don't have nearly as many regrets about games from the 360/PS3 gen or any generation prior.