hero, heroic, outstanding
杰 centers on a person of exceptional quality: a hero, someone heroic, or outstanding in character or ability.
杰 is a variant form of 傑, combining 木 (tree) with 灬 (fire). The original character 傑 uses 亻 (person) and 桀, which likely contributed the sound and the idea of outstanding height. The modern form 杰 simplifies the upper part to 木, but the historical connection to 傑 is clear.
A tree 木 standing above a fire 灬: even in a blaze, the tree remains tall and unburned, like an outstanding hero who rises above challenges.
For ケツ, imagine a heroic figure named Ketsu who always stands out in a crowd: Ketsu -> ケツ, and his name is synonymous with heroism.