Best spells to burn Legendary Resistance?

Quote from Pantagruel666 >>

Quote from Agilemind >>

Faerie Fire is another good one, many enemies don't have good DEX saves and giving every attack on a creature Adv is increasing the total party Damage Per Round by ~40%. Which can trivialize tough encounters.

By the time you're running into bosses with LR, characters tend to average well above the 60% hit chance that gives you a 40% dpr increase, and many of them have alternate ways of getting advantage.

 Not as much as you think, and often it costs them actions / bonus actions to get Adv each turn which provides substantial limitations on what they can do. Only really Barbarian can get Adv for "free" (i.e. at the cost of doubling the enemy crit chance). Not to mention companions & summons which almost never have a way to get Adv. In my experience at high levels only really the Rogue and Barbarian will be getting Adv regularly - and the Rogue is usually using a BA to do so. The warlock might decide it is worth a spellslot and a full action to give themselves advantage but not that often TBH. 

A lot of spells listed also have concentration, which if it doesn’t remove their action economy completely, could just be disrupted by attacking the spellcaster.

I like using Bane on enemies with Legendary Resistance. Lots of scary enemies are bad at Charisma saves, and if they let it go through, they are worse at making all their other saves.