They always say: "Keep your friends close and your enemies closer." But how can you always tell the difference? It's a well-known fact that most of the time, an epic hero's arch-enemies is the hero's former best friend.

How do you know if your bestie is preparing to shove you into an (almost) inescapable death trap? Here are 10 can't-miss signs that your friend is really an arch-fiend.

10) Your best friend starts dating the person you're in love with
This is a dick move, and is always, always a sign your best friend is headed for arch nemesis-dom.

9) Your best friend is way rich
Based on Smallville and Spider-Man, among other things, this is a pretty good sign. If you have humble, but good clean roots, and your best friend is the richest guy in town? Look out.

8) Your best friend has an over-bearing/insane father.
Especially if the father dies/is imprisoned/disappears. And it's your fault. Not to mention if the dad is an actual supervillain, like the Green Goblin. This one often goes hand in hand with the best friend being rich, but a desperate need to please a deeply unpleasant father can also lead a best friend down the evil path. For example, say daddy used to bully and mock his kids for not learning the Great Fireball Technique quickly enough.

7) You have really different philosophical and/or political points of view.
Suppose that you're a dyed-in-the-wool Starfleet loyalist, who's determined to crush the rebel Maquis — but your friend secretly harbors Maquis sympathies and doesn't want to be a tool of the man. Also, expect to see this one show up a lot when X-Men: First Class comes out this summer.

6) You used to share everything, but suddenly your best friend seems to have a secret he's not telling you.
To be fair, you may be hiding your super-hero alter-ego from your friend — but your pal is hiding the fact that he or she is building a death ray. Or your pal has secretly gotten married, against the Jedi code. Or your friend/mentor has secretly hired Afghan guerillas to lock you in a cave and kill you. Maybe your friend has been gone for six years, only to return acting really shifty and cold, and secretly wants to lead the Dragons of Heaven.

5) Your friendship has always had a tinge of the competitive about it
You may think this is friendly competition, but your bestie is beginning to obsess over proving that he or she is better than you. Often, as this TVTropes page points out, friendly childhood rivalry can turn into an adult hatred. That's what happened to Superman and his childhood friend who became Conduit. Plus you could argue that Sinestro starts out as Hal Jordan's friend, but gets threatened by Hal always being the best Green Lantern.

4) Your BFF saw things nobody is supposed to see.
Maybe your chum looked into the Time Vortex, and now your friend keeps hearing a weird drumming that's oddly reminiscent of your theme tune. Or maybe your best friend has died and gotten a glimpse of Hell, and come back wrong.

3) Your best friend gets some sort of physical deformity
Dr. Doom isn't Reed Richard's best friend, but (at least in the movies) they are friends. Anakin, in addition to the crazy Sith eyes, has that scar and missing limb prior to turning against Obi-Wan. There's also Dr. Drakken in Kim Possible, who partly turns against Dr. Possible as a result of all the teasing he gets for his mistakes — but also turns full-on evil after a failed experiment makes his skin Na'vi-blue all over. Bottom line. If your friend so much as gets a hangnail, you should start watching your back.

2) Your best friend has gotten godlike powers.
You passed through a mysterious barrier at the edge of the galaxy, or maybe you encountered some kind of mysterious alien probe. And all of a sudden, your good old pal is having glowy eyes, or knows stuff that a normal person isn't supposed to know.

1) You left your friend for dead.
In which case, shame on you. Leaving your friends for dead is just not cool, and it never turns out well. Even if they actually were dead, and then they got resurrected because Superboy punched the universe. You should have known.