あまりに means exceedingly here, スゴイmeans amazing or incredible, スピード is speed, の is a possessive particle (like Kirby of the Stars), ため is Because of, 光 is light, の as before, を is an object marker, 超えmeans to exceed or surpass.
So like"Because of its exceedingly incredible speed, it surpasses the speed of light"
And for the mfs who think it means time stop, the time stop and this aren't connected. The two parts in the sentence separated by a comma, which in jap functions as a natural pause, indicating that they are related in describing the abilities of Plat but are not causally connected. The sentence does not say that the speed causes or enables the time stop, it's simply listing features of Plat.
Commas are often used to divide separate ideas within the same sentence, the comma is after the speed yap, specifically the word for exceeds/surpasses. Commas can also connect stuff, but how depends on context or added conjunctions (like ので for "because" or から for "so"). If speed and time stop were directly connected, it'd be like, 光の速度を超えることで、この世の「時」を止めることができた or some shit (By surpassing the speed of light, it was able to stop time). It doesn't, there’s no causal wording or connectors or whatever slop to tie them together.
Which is to say, the manga itself flatout says Plat exceeds SoL with sheer speed.