There have been several times when I've seen pornstars performing deep throat and the gagging reflex causes them to tear up. The most infamous person known for this was Jeanna Fine. There was a great scene in Oral Madness (1991) where Jeanna Fine deep throats Sean Michaels to tears. One of her best oral scenes.
For outright balling the first scene that comes to mind was the infamous scene from Anabolic's controversial
Rough Sex 2 (1999) in which Regan Starr breaks down after Mickey G slaps her. There are obviously others from the infamous Meatholes series (e.g. Ashley Blue, Nikki Hunter, Taryn Thomas).
There are other threads related to this topic maybe not as specific. Do a search for "crying" and "rough sex".
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