Meliodas were using the
same smaller Demon Mark when they lost against Dubs and Dahlia, and they used the
same, much larger Demon Mark when they beat Dubs and Dahlia. CBL blatantly shows them
enhancing their marks before the second battle.
The SD fight outright shows that they're equal.
He held back against Supreme Deity (the person that cursed Elizabeth), Dubs and Dahlia just because of brotherly love? I don't buy that for a millisecond, especially since Zeldris already saw him use Trillion Dark against Demon King.
No he does not.
We don't even scale that version of Zeldris to Meliodas, just CBL Zeldris.
He put him on his knees by
concentrating all of his magic into one spot.
Other than that, they were
at least similar physically, though Mael was definitely stronger.
They were battling with darkness and ark weapons the whole time, btw. Plus, where are you getting this idea that Mael relies on magic? In every battle, we see him use both strength and magic, and Escanor's feats suggest that Sunshine grants a similar degree of physical and magical power.
Mael didn't want to, but he
had to. He even slices into Zeldris' back later, and
clearly struggles against rage-amped Zeldris to the point where he's exhausted.
He took him off-guard when he was
exhausted and
focusing totally on someone else.
A) Nanashi was holding back. He's way stronger than just being lower Archangel level.
B) For Zeldris to not be one-shot by Mael, who one-shot Crisis-amped Original Demon, he'd have to at least be on a similar level to True Body Ludoshel.