Well i realize just because it says light doesn’t mean light speed. And i know that earlier in a taizai speed discussion the light concept was debunked but i still stand to reason that sins are ftl . First is the spell exterminate ray. This spell is described as a disintegration beam according to wiki.
https://nanatsu-no-taizai.fandom.com/wiki/Spells ( you will see exterminate ray)
As we know beams travel at light speed based off of statements of scientist and google. We have also seen characters react these beams like chandler.
As you can see above merlin fires her beam then chandler reacts and fires her beam. And before anyone says "if it was actuallu sol then merlins beam would have been closer to to chandler since he fired first" Chandler's beam was a lot more powerful(as you can see in the size difference) so it overpowered her beam and pushed it back.
Another point is Zeldris's ominous nebula. It was flat out stated to be faster than light.
People try to say what ludociel said was a hyperbole/idiom but to debunk that he literally said that it is not an exaggeration which is literally what a hyperbole is.
Characters like mael have also reacted to this speed feat also.
As you can see he casts it pulls his sword and melted zeldris's blade.
We can also use mael's attack :arrows of salvation. This attack is a literal ark beam.
king could not react to the beam in this show but
AS you can see he easily reacted to it then.
This statement proves my point also -
It says the goddess race uses light particles. It is a proven fact that light particles move at light speed no matter how you try to debunk it.
I have seen people say that it did not look like it was a reflection off of diane's skin but Light has been proven to be able to bounce off of things too. And even so it is fiction, the author is not going to draw a literally reflection of light. Plus not everything is always going to be consistent in any show People ALSO say that the light curved so it is not actually light. The goddess race literally manipulates light. They have made various objects out of light too. For example mael's light saucers.
And at the end , even you try to debunk all of that we still know that a beam moves a light speed.(look it up)
The gray demons shoot beams from their mouth. (
https://nanatsu-no-taizai.fandom.com/wiki/Gray_Demons)(states they can use beams right above abilities)
(one doing it)
And nanshi does this
Better manga version below
Clearly reacts to a beam right there and many characters scale to an above a to him.