我々(us angels)はアマツ様の教えを順守して行動する。でも人はちがう。アマツ様の教えを我欲がしのぎ、憎み、欺き、決して足りず争いを繰り返す。
amatsu-sama's teachings are usurped by selfishness, hatred, deceit, (??) isn't sufficient, the fighting repeats endlessly.
angels have been teaching the humans stuff, and will soon leave the humans to be independant
What is "決して足りず" in this situation? is it 様の教え? 我々の行動？ 我々? or something else?
is [憎み、欺き、] under 教えを我欲がしのぎ? ie. 教えを[憎み、欺き、我欲]がしのぎ?
This 足りず is the same as 満ち足りず or 満足せず ("(while) never being satisfied"). This sense of 足る is relatively rare in modern Japanese, but it's a traditional meaning of 足る, and it should be listed in any monolingual dictionary. 足るを知る is a well-known set phrase.
足る
［動ラ五（四）］
１ 「足りる」に同じ。「配慮が―・らぬ」「一見するに―・る」
２ 満足する。「―・るを知らざる者は富むといえども貧し」
Note that 我欲 is merely a temporary subject of the first half of the sentence including 凌ぐ. The implicit main topic of this sentence is 人 (humans), which is indicated in the previous sentence. 憎み can work as a noun ("hatred"), but in this context it's just 憎む's continual form in its literal sense.
アマツ様の教えを我欲がしのぎ、(そして、人は)憎み、欺き、決して足りず争いを繰り返す。 (Human's) selfishness surpasses the teaching of Amatsu; humans hate, deceit and repeat fighting, never being satisfied.
