I'm going to leave a friend at a bar
Why would you want to leave a friend at a bar?
They keep making unwanted advancements on me.
If a friend is counting on you to be with them while at a bar, it is unsafe and rude to leave them behind. If you want to end the friendship, do so in a safer environment.
I kind of agreed with what you said so I decided not to leave them at the bar. I ended up leaving them at home while they got drunk, puked, and fell asleep.
I am sorry you had to go through that. When they sober up I think you should tell them how it makes you uncomfortable.