Some interesting genielock combos

[Greywander]

Specifically regarding the Genie's Wrath subfeature. This subfeature allows you to add damage equal to your proficiency bonus to one attack per turn (your turn only, sorry OAs). It's not a lot of extra damage, but what's interesting is that it adds a specific type of damage instead of just more of the same damage type. Depending on what kind of genie your patron is, you can add either fire, cold, thunder, or bludgeoning.

I'm not aware of any interesting combos that use cold damage.

The fire damage can stop a troll's regeneration. Something like a fighter who has multiple attacks only needs to land one blow in order to negate regeneration. A 1 level dip into genielock is an excellent choice for a character built around troll slaying, as any attack you make can add fire damage. If you cast an attack spell, it can also trigger Flames of Phlegethos, although since the damage is a flat amount rather than rolled, the only benefit is wreathing yourself in flames that damage melee attackers. Maybe use this with a build who's primary attack is Booming Blade or something (you could use GFB, but BB works better against fire resistant/immune enemies).

Storm sorcerers might also consider a dip, as now any attack spell of 1st level or higher will trigger Heart of the Storm by adding a bit of thunder damage. Sadly, Tempest cleric procs off of lightning damage, not thunder.

Choosing bludgeoning damage allows you to use the Crusher feat with any attack, including spells. Sadly, we can only add bludgeoning damage to one attack per turn, so that attack specifically needs to crit in order to activate the last bullet point of Crusher; critting on, say, one of the other beams of EB won't cause the effect.

Keep in mind that you only need a 1 level dip to get this feature, so you can get a lot of mileage out of any effects that trigger on dealing fire, cold, thunder, or bludgeoning damage.

[ATHATH]

Choosing bludgeoning damage allows you to use the Crusher feat with any attack, including spells. Sadly, we can only add bludgeoning damage to one attack per turn, so that attack specifically needs to crit in order to activate the last bullet point of Crusher; critting on, say, one of the other beams of EB won't cause the effect.
Can't you just opt to not add the bludgeoning damage to an attack unless that attack is a crit (or the last attack of your turn)?

[Greywander]

Yes, but you could miss with that last attack. Mostly, you're probably doing this for the 5 foot push (which is also only once per turn, so that works out well), which, when slapped onto an Eldritch Blast with Repelling Blast, increases your total push distance up to 45 feet. I could also see doing something like a TWF build where you have a slashing weapon in one hand and a piercing weapon in the other, and this way you can benefit from all three feats at the same time.

[Nagog]

Those are very good points, I'm a big fan of this idea. My first thought was Celestial Warlock, but since they're both Warlocks it's not entirely viable. I do like the idea of combining Crusher with Slasher on a single attack. Reducing movement speed and moving them 5 feet away, on something like a Rogue, would be great for hit-and-run tactics: They can't chase you very easily, and when you hit them and deal your damage, you don't need to Disengage unless they have a reach weapon because they've been moved 5 feet away.