Opportunists are recognized by their inclination to take advantage of an ongoing course of events for their own benefit. They are self-centered villains who place their own personal gain above all else; will gladly exploit any given situation to suit his or her means; will commit crimes as and when it suits them to do so; and will break and form alliances on a whim in order to succeed. Simply put, if an opportunity arises, they will grab it.

They are similar to Egotists, though they are not exactly the same as Opportunists may not necessarily have excessively high opinions of themselves. They are the opposite of Anti-Villains and Delusional villains, as those types of villains believe their goals are in the best interest of others. However, in rare cases a Delusional villain may also be an Opportunist if their delusions are just a way for them to justify their self-centered goals, an example being Light Yagami.

They are commonly Neutral Evil or Chaotic Evil, but they may be Lawful Evil instead if they take advantage of any given situation in order to gain power for themselves, usually with the aim of oppressing others in the process.

Due to its very nature, it is extremely rare for Opportunists to be Honorable; anyone "of their word" or obsessed with "playing by certain rules" is also unlikely to qualify as they would value alliances or a fixed plan over Opportunistic thinking.