Biting the hand that feeds: Taliban, Saddam...

Evil begets evil. Always. Examples abound from recent history relating to vested interests.

1980's: LTTE is funded by the Indian state, partly to offset the US influence in Sri Lanka and partly due to ethnic relations in that country. Things fall apart, LTTE decides India has done enough and assassinates a senior politician, India washes its hands clean of the issue till very recently.

Saddam Hussein: An ally to offset Iran, he recieves copious amounts of aid resulting in a long war. Saddam goes too far ahead and the US decide he has had enough: Gulf war restricts him.

Iran itself, is an example. 1953 the Shah is installed after a CIA coup to remove the anti-West government, with oil installations in mind. 1979 an Islamic revolution exiles the Shah, making conditions even worse for the West.

Al-Qaeda is one of the groups formed out of US support to Mujahideen fighters during the Soviet invasion of Afghanistan, then bin-Laden not liking the presence of US troops in Saudi Arabia and bombing the Embassies in Africa.

Taliban are a group supported by both the Pakistani and the US military. Just now, the Taliban is retaliating against Pakistan itself, the Army is fighting to evict them from an occupied valley.

More examples welcome in the comments.