Moral dilemmas and temptations, duty and responsibility, relationship friction

The character cheating to win an election and prevent a despot from assuming power
A narcotics officer sampling drugs to maintain his cover so he can bust a drug ring
The character sleeping with someone to gain their trust and find damning evidence against them
Voting for a despicable politician because his policies or ideals are better than his rival's
Beating someone up to get information from them to solve a crime or save a life
Stealing from a corrupt employer to provide essential supplies for suffering people
Allowing one person to die to save a city full of people
Framing a corrupt employee to save the company from ruin
Planting evidence or lying under oath to make sure a guilty person doesn't go free
Murdering a known child abuser or rapist
Spiking an enemy's drink to get them temporarily out of the way so the bigger plan can proceed
Breaking a promise to never again be involved with certain activities or people (because doing so allows the character to right a wrong)
Pretending to like or agree with despicable people so the character can avoid scrutiny and continue with their underground operation

The character needing to cozy up to people they despise
The character having to become intimately involved with the people they're working against 
The enemy becoming suspicious of the character
Being insulted or criticized by those who don't know about the character's ulterior motive
Needing to sneak out at unusual hours without raising suspicions
Having to dodge questions about what the character is doing and why
The character being confronted by a beloved friend or family members about their actions
Being questioned by the police
Having to keep the plan secret and go through it all alone