Relationship friction, failures and mistakes, losing an advantage, ego-related conflict

The character being framed by a trusted co-worker to cover for their own mistake
Being set up by a friend or loved one to take the fall for their crime
Being abandoned by an ally in a life-threatening situation, such as a battle, violent confrontation, or extreme weather event
Being forced out of a shared business by a long-term partner 
A best friend not standing up for the character who is being publicly embarrassed or bullied
A friend revealing a closely held secret (the character's sexual orientation, an embarrassing mistake from the past, their involvement in a crime, etc.)
Being dumped by a friend when it suits their purposes (because a better "friend" opportunity came along, because sticking with the character through a troubling time is too much work, etc.)
The character learning an ally was never really on his or her side

A framed character having to prove they did nothing wrong
Loss of credibility with employers due to the co-worker's lies
Running into the former friend at social events or a shared favorite gym or coffee shop
Financial complications and loss of time from having to unwind a long-term business partnership
Embarrassment when a video capturing the betrayal or confrontation goes viral 
Legal complications (if allegations of a crime are involved) 
Losing the friend but still having to work with him or her
The inconvenience of having to replace the ally or partner
Temporarily putting other goals on hold to stabilize a business after the partner's departure