Kamado Tanjiro no Uta - Go Shiina (Episode 19 Demon Slayer ED probably has spoilers i dunno i just like the powerful-ness of the song)
The song expresses strength but it carries a sad heaviness with the orchestra. Even though in the beginning it begins quietly, consider that part as me ranting to the player about my sadness and why I will defeat them. At 1:39 in the video that's when it starts to pick up and the battle becomes harder. The danmaku you'd have to dodge, becomes harder to dodge as they are shot in tight packs releasing in bursts to show all the sadness and anger I've kept bottled up. I would probably be a stage 1 or 2 boss ngl.
Okay... might've overdone that but hey that was fun to write.