A bad pimple can be characterized by being large, red, swollen, and possibly filled with pus. It may feel tender or painful when touched and can be quite noticeable on the skin. If you are concerned about a pimple that looks particularly bad, it’s best to refrain from picking or squeezing it to prevent potential scarring or infection. Topical acne treatments and keeping the skin clean can help in improving the appearance of pimples.