Success is relative, evil isn't. Success is merely acheiving a goal, so it is morally neutral. The goal itself can be good or evil, or morally neutral.

Examples:

goal is 100 push ups. Morally neutral
goal is 100 murders. Morally evil.
goal is 100 lives saved. Morally good.

Your actions taken in order to achieve your goal can be good, evil, or morally neutral as well.

In your example, the drug dealer's goal was to be wealthy. (implicit in your statement) He achieved success in that goal by selling drugs tha ruin other people's lives. (morally evil) He has achieved success in his goal, which is morally neutral, by doing something morally evil.