Lightning is actually around Mach 1,282, as per this wiki. Aside from that, I never knew anyone would actually try using any of the RoTMG characters for matchups anymore; reminds me to revise the classes' 8-C+ keys due to lightning's new AP and another issue regarding how it was scaled.
LotLL should be faster than lightning if I'm correct,
seeing that a knight slowed down by water is roughly comparable to them. So he definitely has a speed advantage by comparison.
Muruem is 1.45 Megatons AP-wise, and his durability is around that level, too (assuming the rose bomb that severely harmed him is comparable). LOTLL is around 8.16 Megatons scaling to the Rock Dragon,
who is this powerfu according to a calc, and rather casually at that durability-wise (the amount of damage the ramming attack deals is very low in comparison to his durability), and his AP stemming from the normal attacks he uses should be somewhat superior or comparable to the Rock Dragon's ramming attack.
So, as per what you mentioned in the OP, LoTLL has it physically, as his durability and AP is rather threatening as compared to Meruem's.
At this point, it generally depends on how Meruem would start off. If he tries getting close up, then LoTLL just shotguns him with his laser attacks or his summons. If he tries to play it safe and attack him from a long range, then It'll take an absurdly long time but he'd possibly win with a lot of difficulty (and patience).
