“The person with great anger.” Different versions have tried different English words to catch the sense of the Hebrew, including “hot-tempered” (NIV), “violent tempered” (NRSV) and “hothead,” (Waltke). A person who breaks into anger and wrath when things do not go his way will continue to be that way, no matter how many apologies he makes after he has calmed down, and no matter how much he says it will not happen again. There needs to be some genuine transformation, which takes great effort and almost always outside intervention and counseling.
“will bear the penalty.” Here, a “penalty” is being used by the figure of speech synecdoche for all kinds of punishment. This is the way to “wake up” an angry person. Let them bear the penalty of their action. Bailing them out of the problem they have created does not help.
“Surely if.” The Hebrew can be “for if; indeed if; surely if,” etc. Here, “surely” catches the sense of the verse (cp. Waltke; Proverbs).
“you will do it again and again.” This seems to be the sense of the Hebrew text, as shown in the versions. However, the Hebrew text may have more meaning as well, because the word translated “again” in most versions also means “to add.” Thus, the Tanakh translation by the Jewish Publication Society ends the stanza not with, “you will do it again and again,” but with “you will only make it worse,” i.e., by bailing the person out and not letting him pay the penalty, you only make the situation worse. Many counselors would concur with that, and thus the Hebrew of this proverb is a beautiful double entendre. The “helper” will have to help again, and by helping actually only makes the situation worse.