Beware Of Your Enemies

Noun opponent in a conflict or contest
“Fear is your best friend or your worst adversary. It’s like fire. If you can control it, it can cook for you, it can heat your house."
Noun bitter enemy, especially one who seems unbeatable
Marni, a new Vice President of a large Public Relations Agency, is returning home for her brother Will's wedding. Marni discovers that his bride Joanna is her former arch nemesis in high school who made her life a living hell
Noun somebody's main or worst opponent in a contest, conflict, or dispute
Ex-special operative MacGruber is called back into action to take down his archenemy, Dieter Von Cunth, who's in possession of a nuclear warhead and bent on destroying Washington, D.C.
Noun enemy or opponent
Jack Sparrow races to recover the heart of Davy Jones to avoid enslaving his soul to Jones' service, as other friends and foes seek the heart for their own agenda as well.
Verb associate or form a friendship with someone, esp. when one is not supposed to
"Nobody will ever win the Battle of the Sexes. There's just too much fraternizing with the enemy."
Noun member of a small independent group taking part in irregular fighting
This mysterious martial arts is used by Japanese guerrilla fighters. Ninjitsu teaches a variety of ways to surprise and beat your opponent, with the direction to kill.
Noun bitter enemy, especially one who seems unbeatable
What a difference a TV show makes: Rosie O'Donnell's biggest nemesis of the year, Donald Trump is prepared to make nice with the acid-tongued talk titan, as long as she comes on his show.
Noun purposely destroy, damage, or disrupt
The Ministry of State Security (MSS) ensures security against enemy agents, spies, and counter-revolutionary activities designed to sabotage China's socialist system.
Verb speak boastfully to an opponent
Fantasy sports, the process of drafting teams, betting on the success of individual players and trash-talking with your similarly obsessed friends has become a billion-dollar business on the Web and mobile devices.
Noun principal bad character in a film or work of fiction
Christopher Nolan has announced that the next chapter in his Batman series will be called "The Dark Knight Rises," though he still refuses to name a villain.