As Harrison Ford himself stated during an interview, the relentless emotional undercurrent of Kimble's grief for his wife:
Kimble's thoroughly haunting nightmare about his late wife, which starts off all good and romantic, then abruptly segues into his desperate, futile attempts to revive her, then holding her in his arms as she already died.
Helen Kimble's 911 call—her voice weak and shaky, her pleas for her husband Richard to help her. A literal example of this trope, as he is seen crying as it's played in court — where it's being used as evidence against him.
Helen's death in general. Richard just came home from a charity party, there were rose petals all over the stairs leading up to their room so it was implied that his wife was waiting for him to come home so they could have sex. Only for him to find her dead and Sykes still in the house.
Kimble breaking down during the interrogation as the full impact of what's happened (his wife has been murdered) and what's going to happen (he's being blamed for it) starts to hit him. The cops mocking, taunting tones really don't help.
Kimble pleading to Gerard, "I DIDN'T KILL MY WIFE!". The man is just desperate for somebody, anybody to believe him, and Gerard responds with his infamous "I don't care!" (makes the Meaningful Echo at the film's end that much more). For a split second, it looks as though Kimble is seriously contemplating killing Gerard, possible figuring he has nothing to live for anymore and that he might as well be executed for something.
In the midst of beating up his treacherous friend, Kimble pauses for a moment to sorrowfully ask, "Why Helen?", not understanding why his innocent wife had to die because of some conspiracy she knew nothing about.
Kimble Cry Laughing when Gerard tells him that Nichols lets Sykes into his house, realizing that his wife would still be alive if he hadn't done something as simple as loan his friend his keys.
Even with Richard's innocence proven and the guilty men caught, at the end of the day, his wife Helen is still dead, and nobody is going to be able to change that for Richard.