almost, quite, really
殆 centers on being at the edge of completeness: almost, nearly, or quite. It can also describe a situation that is really or extremely close to a limit.
殆 combines 歹 (death/danger) with 台, which likely contributes the sound. The idea of being near death or danger may have led to the sense of 'almost' or 'nearly'.
The left side 歹 suggests danger or death, and the right side 台 looks like a platform. Imagine standing on a dangerous platform, almost falling off—you are nearly at the edge.
For タイ, picture a tie holding you back from the edge: tie -> タイ, and you are almost falling but the tie keeps you safe.
almost; nearly; mostly; practically; virtually; basically; just about; all but
quite; utterly; really; completely
danger; jeopardy; distress
to face danger; to fall into crisis
if you know your enemy and know yourself, in a hundred battles you will never be defeated; know your enemy
hardly any; almost nonexistent; very little