afterthink

As a noun remorse

is a feeling of regret or sadness for doing wrong or sinning.

As a verb afterthink is

to think about after the fact, reflect on.

As verbs the difference between repent and afterthink

is that repent is (label) to feel pain, sorrow, or regret for what one has done or omitted to do; the cause for repenting may be indicated with "of" while afterthink is to think about after the fact, reflect on.

As an adjective repent

is (chiefly|botany) creeping along the ground.

As verbs the difference between reflect and afterthink

is that reflect is to bend back (light, etc) from a surface while afterthink is to think about after the fact, reflect on.