Completely
Entirely, Truly, Really, Wholly
adverb
This is the adverb version of the kanji all. So, it's like you add an 'ly' to it. But, that doesn't work too well (allly? c'mon). So, instead think of this word as completely, entirely or one of the other definitions listed above.
まったく
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
The person who completely doesn't understand this vocab word is Matt (まった). Be sure to take note of the small っ, too.
これじゃあ、全く話にならないよ。
If you're going to be like this, then I can't take it seriously.
コウイチは、全く見かえりをもとめずに人助けをします。
Koichi never asks for anything in return when he helps people.
コンドームも全く安全だって訳はない。俺の友達はゴムを着けてたけど、軽トラにはねられたしな。
Condoms aren’t completely safe. My friend was wearing one and got hit by a pickup truck.