償い means “atonement,” “reparation,” or “making amends for a wrong.” It carries a deeper, more serious nuance than simply saying “sorry,” suggesting that someone must take responsibility and pay a price for what they have done.
In the song, この身を滅ぼしてこその償い means “only by destroying this body can there be atonement,” giving the word a dramatic and powerful emotional weight.
BE:FIRST's "It's Not A Bad Life" is a shrug and a snarl at the same time. The English hook, "If I die, I die", sounds careless, but the Japanese verses show a guy who has stopped asking anyone for permission to be himself. Early on he asks "誰が決めて誰が裁くの?" (Who decides, and who judges?), and he is openly mocking the idea that ordinary people get to rule on right and wrong.
The scars are the point. He talks about "傷だらけの背中には" (on my back, covered in scars) where "刻まれた愛とプライド" (love and pride are carved). He admits his real self isn't pretty, that what's under the skin is not something you show people, and that lies left alone fester like an infected wound. That image is a bit gross, and it works. Then comes the line I love most: "檻の外で生きる獣でありたい" (I want to be a beast living outside the cage). The verb 喰らい尽くそう in "光も影も 喰らい尽くそう" (let's devour it all, the light and the shadow) is a rough, hungry way of saying "eat", so he swallows the good and bad in himself whole. By the end he drops the need for stability and decides to push his love through, which is why "Everything is alright" lands as a choice rather than a comfort.