curse, haunt
祟 centers on a supernatural affliction: a curse or haunting that brings harm or misfortune, often as a consequence of angered spirits.
祟 combines 出 (to come out) and 示 (altar, spirit), suggesting a spirit emerging to cause harm. The exact historical development is uncertain, but the component combination fits the meaning of a curse or haunting.
A spirit (示) comes out (出) from the altar to haunt and curse. Picture a ghost emerging from a shrine to bring misfortune.
For スイ, imagine a cursed swing (スイ) that moves on its own, haunted by the spirit that came out of the altar. The swing's eerie motion cues スイ.
curse; divine punishment; wrath (of an angry spirit)
to curse; to cast a spell; to haunt; to torment
misfortunes never come singly
the evil eye
powerful evil spirit that brings calamity; supernatural being that brings disaster
let sleeping dogs lie; wake not a sleeping lion; the spirit you do not approach will not curse you