Answer:
Three little letters, a paradox to some. The worse that it is, the better it becomes.
Gets rid of bad ones, short and tall. Tightens when used, one size fits all.
If you break me, I do not stop working. If you touch me, I may be snared. If you lose me, nothing will matter.
i'm popular for Knuzlocks what am i
Long and think, red within, with a nail at the end.
Iβm grown from darkness but shine with a pale light. Very round I am and always a lady's delight.