完 - COMPLETELY Protected, PERFECTLY Safe

Readings & Meanings:

カン

complete, perfect

Common Usage:

完璧

完全犯罪

完了

Examples:

完璧に覚えるまで繰り返し練習する。

完全犯罪を取り扱った小説を読んだ。

今日の勉強はこれで完了だ。

Translations:

I practice by repetition until I remember perfectly.

I read a novel about the perfect crime.

Today's studying is at an end.

Radical:

宀, U-kammuri, the U-crown tops this as the radical.

元 is the phonetic. It's a pictograph of somebody thrusting their head high (in 兀) and another line thrown in after 兀 lost its meaning.

In 完, though, the 元 shows a round thing, an encirclement. This plus a roof means a building that is completely protected. Thus, "complete."

References:

http://www.kanjinetworks.com/indices/radindex.html
http://www.thejapanesepage.com/node/kanji/7.htm