Mobile games that have waiting as a mechanic. Like you can only do so much, then you need to either stop or pay. I realise this is a much hated genre already.

Back when Clash of Clans was big, I’d have students sleep through the entire day. I’d call the mum, “please take all phones and computers from your child’s room after 8pm”. After that the kids would absolutely hate me, but they’d be awake for school.

Back in the 00’s, when Travian was big. Travian was basically Clash of Clans with worse graphics. I’d go on holiday with a girlfriend, and I’d have to pop in an internet cafe every 2 hours to spend resources or my city would be fucked.

Drip feeding progression in order to incentivize buying microtransactions.

Sexism.

Tiered items in any RPG. Most RPGs are about cycling through random items you find over and over again. Either make everything have really similar stats but with different special effects or uses, or do it like MGSV where you unlock upgrades as you go that basically add features to existing stuff. Warframe is probably the best example. It has good items and bad items, but there are only like 3 weapon tiers and every weapon just works completely different and for different scenarios. Obviously a lot more work to implement than just randomizing the stats on the same item, and not quite as addictive, which is often the purpose when it’s a free-to-play game.