I never said he's immune to commandments. What I said is that I don't see him getting afflicted by them during the battle. And no, Mel is immortal via longevity too. If he was only immortal via resurrection and hadn't an indefinite lifespam he would age, but no, he remained in his child form since the beginning of the curse. At least, that's what I understood. Plus, Mel doesn't need to kill them, he can incapacitate them so the commandment doe
Meliodas is not immortal via longevity.He's a midget.He isn't going grow any more.He has an average demon lifespan since nothing indicates otherwise.
He still has to worry about Piety,being trapped by Greyroad which would severely restrict him,stuff that can be summoned like bugs,low tier demons,zombies which he could accidentally kill.
They fight and they win? There is not much I can say about that.
How do they win when they're at such an overwhelming disadvantage against the AAs?
The Archangels have flight which means Diane isn't even landing a hit on them.
The Archangels have insane regen which means they can't be put down permanently.
They have amazing defences like Tarmiel's water intangibility and
Sariel's wind barrier.So tagging their actually bodies might be impossible for these two.
Their Graces can absolutely shred characters on their level.And neither King nor Diane are well known for their regen.
Don't see how the Archangels lose this.
I have really not been impressed by Derrierie. Combo Star is powerful but also very limited, she can only do close range attacks and Dolor has strength, resilience, agility, can boost his defense, read hearts. Ground is also more versatile.
Meliodas is a better fighter than Derrierie, not only he had his sword. But at 56K he was able to overpower Dolor(54K) and Gloxinia(50K). At 60K he overpowered Derrierie as well. Derrierie is not as skilled.
Derierre has flight which gives her an incredible mobility advantage over someone like Dolor.Ground isn't going to be very effective due to that fact.Derierre also has regen and darkness constructs.
Almost everyone in the series is less skilled than Mel..

Derierre isn't fighting Mel here.She fighting Dolor.And Derierre is more skilled than Dolor in cqc.
Dolor got oneshotted by a dude with 47k strength and ragdolled by a dude with 50k strength.Derierre is packing 48k strength which is further complimented by her magic,Combo star.
He's going be in a world of trouble if she lands a single good hit on him.
Even if he shells up with Heavy metal,he'd still lose.He won't be able to move or attack and his magic would run out eventually.The damage is just going to continue increasing and accumulating overtime until he's unable to take anymore.