>>721088836
Bosses rewards (not counting progression items that aren't also useful), SPOILER obviously
Hollow Knight:
Gruz Mother: geo
False Knight: a chest full of geo
Brooding Mawlek: mask shard
Hornet: new ability
Mantis Lords: a chest full of geo and a charm
Soul Master: new spell
Watcher Knights: nothing
Flukemarm: charm
Dung Defender: charm
Crystal Guardian: nothing
Enraged Guardian: mask shard
Broken Vessel: new ability
Nosk: mask shard
Hive Knight: charm
Collector: some grubs and the grub map
Hornet 2: nothing
God Tamer: a fuckton of geo
Traitor Lord: nothing
Uumuu: nothing
Grimm/NKG: charm
Final bosses: nothing
Silksong:
Moss Mother: nothing
Bell Beast: silk heart
Skull Tyrant: rosaries
Skull Tyrant 2: nothing
Lace: nothing
Forgebrothers: nothing (i think)
Savage Beastfly: crest
Fourth Chorus: nothing
Savage Beastfly II: mask shard (i think)
Moorwing: nothing
Sister Splinter: nothing (you get a new ability shortly after, but there are still enemies and platforming to do after the fight)
Widow: new ability
Mossmother duo: blue tool
Great Conchflies: nothing
Last Judge: nothing
Phantom: new spell
Cogwork Dancers: nothing
Second Sentinel: blue tool
Trobbio: blue tool
The Unravelled: silk heart
Groal the Great: nothing
Broodmother: rosaries
First Sinner: new spell
Enraged Cronchfly: red tool
Father of the Flame: blue tool
Chef Lugoli: ingredient (=1/5 of a pale oil)
Lace 2: silk heart
GMS: new spell (if you unlock Act III and come back there)
Bell Eater: new ability
Trobbio 2: blue tool
Voltvyrm: blue tool
Pinstress: blue tool
Gurr the Outcast: mask shard
Crawfather: the craw nest thing that gives rosaries and shards
Karmellita, Khan, Seth, Nyleth, Palestag and Clove Dancers: nothing x 6
Lost Lace: nothing