The End; Finis
Used at the end of a novel, film, or similar work to mark its conclusion. Often appears as a standalone caption.
映画の最後に「完」の文字が映し出された。
At the end of the movie, the word 'The End' appeared on the screen.
Attached to nouns to indicate that something has been completed or finished. Common in compounds like 工事完了 (construction completed) or 任務完了 (mission accomplished).
工事は来月完了の予定です。
The construction is scheduled for completion next month.
full provision; fully equipped
Used in compounds to indicate that something is fully provided or equipped, such as 冷暖房完備 (fully equipped with air conditioning and heating).
このアパートはエアコン完備です。
This apartment comes fully equipped with air conditioning.
完了 is the free-standing noun/verb meaning 'completion', while 完 is the bound suffix used inside compounds like 工事完了.
未 is a prefix meaning 'not yet' (as in 未完), the opposite of 完's sense of something being finished or fully done.
From Middle Chinese 完 (hwan, 'complete, finish'). Used as a suffix in Japanese to indicate completion or full provision.