demolition, break, destroy
壊 centers on breaking something down physically or structurally: demolition, destruction, or breaking an object. The idea extends naturally to ruining or spoiling something.
壊 is the modern simplified form of 壞. The older form combines 土 (earth) with 褱, which likely contributed the sound and the idea of breaking or ruining. The modern right side is a simplification.
The left side 土 (earth) suggests something solid, while the right side looks like a structure (十 on top, ⺫ as a net or enclosure, and 衣 as clothing at the bottom). Imagine an earthquake breaking the earth and demolishing the structure, tearing the clothing at the bottom.
For カイ, picture a demolition crew swinging a giant hammer and shouting 'KAI!' as they break the earth and structure apart: KAI -> カイ.
destruction; disruption
to be broken; to break; to fall apart; to collapse; to be destroyed; to be damaged
collapse; crumbling; breaking down; caving in
to break; to destroy; to demolish
(complete) destruction; annihilation; devastation
destruction; collapse; crumbling
damage; destruction
burst (e.g. dam, embankment, levee); breach; collapse; washout; rupture
destruction; demolition; smashing apart; tearing down
necrosis
demolition; pulling down; destruction; dismantling
to destroy; to break (by striking); to smash; to knock down
complete destruction
partial destruction
disintegration
to demolish; to tear down; to pull down
non-destructive
gangrene
destruction; demolition; smashing apart; tearing down
alpha decay