Based on the setting explained by KorvinStarmast in this question, I'd like to know if you can pull someone more than once with Eldritch Blast + Grasp of Hadar if you hit him with multiple blasts (meaning multiple beams or multiple casts of the same cantrip).
The spell description states that you shoot multiple beams as you level up instead of shooting a stronger one, kinda like the Magic Missile spell, which have been ruled by Jeremy Crowford to work a little different from other spells in terms of calculating some effects like the bonus damage from Empowered Evocation like noted in this answer.
I'm aware of the diference in spelling between Grasp of Hadar and Repelling Blast, probably due to 3D combat, but I'm not sure that is really intended to work like that if, for example, you cast it twice in some way.
Best Answer
No, you can't (at least not on the same turn or round)
Grasp of Hadar explicitly states (emphasis mine):
If you absolutely want to pull a creature up twice in a round, you can multiclass into Sorcerer and combine Grasp of Hadar with a quickened Thorn Whip cantrip (which you need to have gained by choosing Thorn Whip as a Tome warlock, since neither Warlocks nor Sorcerers have access to the cantrip otherwise).
In my opinion, that's not really worth it, though, since you need at least 3 levels in Sorcerer in order to do this once per day, unless you convert your Sorcerer spell slots into Sorcery points for a total of 3+8=11 sorcery points, or 5* per day. Honestly, at that point, you're probably better of going for sorcerer + whatever gives you access to Thorn Whip, since that cantrip has no restriction on times/turn, unlike Grasp of Hadar.
Another option is multiclassing into Druid, Ranger or Bard in order to get access to Grasping Vine, but that's a level 4 spell that has to be anchored to the ground, meaning that you can't pull enemies up and drop them for fall damage unless there's a conventiently placed cliff around on the edge of which you could attach the spell. Either way, multiclassing 7 levels into e.g. Bard (which would suit a Warlock best due to a shared spellcasting ability) for this purpose alone is just absurd (maybe even Abserd).