I like how author manages character deaths. When first time introduced, I thought pillars are invincible, but then they killed Flame Pillar in his first arc with his own character arc left unfinished. This was a surprise. After that, when they started to go into Sound Pillar's arc, I genuinely believed they would kill him, too. But, no. His character arc is finished, he retired, and hapilly ever after.
I also like how every battle is a hopeless one.