That depends on your goals. There isn't one single answer. A sound investment for one person is a bad investment for another person. You need to consider what's a good investment for your situation. This will depend on your goals, appetite for risk, age, and investment experience.
Shares in a growth-oriented business might be a good investment for a 35-year-old business owner. High-dividend shares, fixed-interest investments, or term deposits might be good investments for a person no longer working. It all depends on the situation.
It’s easier to define a bad investment. A bad investment is one in which you have no idea why you invested, no understanding of the underlying asset or business, no idea of the risk involved, and no idea how long you should be holding it.