Remathilis
Legend
The biggest abuser is warlock, since they get two spell slots of the highest level from levels 2 to 10. In theory, if they were able to rest every combat, they would never suffer spell attrition. Having two fourth or fifth level spells every fight at level 9 is powerful....what class besides wizards can "abuse" short rests?
Additionally, the warlock is able to abuse multi-classing, particularly with sorcerers and paladins, to use their spell slots to fuel smite and sorcery points.
Honestly, the half-caster warlock fixes both these problems, but if that's not in the cards, the best bet would be to limit recharge of pact magic to 2/day and make one of them a free "1 minute" recharge like the monk gets. It's a bandaid, but it makes the warlock more consistent and less prone to abuse.