The big boys were ruthless (mean) to the little boy.
The core word is 'rue', or to regret. So ruthless is without regret, and rueful or ruefully is with regret.
there is no such word in German
Plick is not a German word.
greave is not a German word.
But isn't a German word.
Rouse is not a German word
"houpacker" means nothing in German; it is not a German word.
Oxded is not a German word
That word is not German, sorry.
Do you mean elan? Then the word exists in German
Sunna is not a German word. The closest German word is Sonne which translates as sun.