The speaker is talking to someone they can't hate, and they wish they could. Hatred, as they describe it, is powerful: it "moves mountains and ends lives" in a wild blaze nobody can put out. It would at least give them force and motion. Instead, they feel fear, which holds them down like chains. The odd, painful detail is that they are "begging for the end," so the fear seems to leave them stuck, wanting the whole situation to be over without being able to act.
What remains is "a spark of what could've been," a small image that sits against the big blaze of hatred. The spark suggests a lost possibility, maybe a relationship or a future that never fully happened. The mood is quiet, tired, and sad. The lowercase, short lines make the speaker sound worn down and a little defeated, as if even anger is out of reach.