If he had expressed any of this guilt,
No. Because James didn't… stop pushing Severus around in their seventh year. James (and Sirius Black) kept hexing Severus because Severus was a “special case.”
James didn't apologize to Severus. Neither did the other Marauders.
James' rivalry with Severus Snape also started early when he insulted the wizard while on the Hogwarts Express. Since then, James and his friends, also known as the Marauders, taunted Snape throughout most of their schooling.
It was a shock for Harry to see his adored father behaving like a bullying teenager. He felt badly for Snape having been on the receiving end and the fact that Harry could relate to Snape's experience must have made it even more difficult for him.
The acclaimed author explained that Harry paid tribute to Snape because of “forgiveness and gratitude.” Though Snape bullied Harry, he also saved him. “Harry hoped in his heart that he too would be forgiven.
Because Lily (according to them) had the nerve to not fall in love with her former childhood friend, Severus Snape and marry that no-good-evil-spoiled-rich-brat James Potter.
Severus Snape spent the majority of his life in love with Lily Potter. It is easy to understand why Snape, who had an unhappy homelife as a child, fell hard for the first person to show him love and kindness.
He hated Snape for being uppity and challenging those of higher status while being obviously of low status. A person of the wrong class stepping out of bounds must be put in their place.
Hogwarts Years
James fell in love with Lily from the moment he first saw her on their first train ride. James was especially delighted when they were both sorted into, in James' opinon the best house ever, Gryffindor.
"I regret it," said Voldemort coldly. When Voldemort finally works out the truth about the Elder Wand (albeit incorrectly) he sends Lucius to fetch Snape and then confronts him before killing him off. He confesses his apparent “regret” for having to kill him, twice.
But Snape didn't have time to get too deeply into that. Later in the year, Dumbledore revealed that Harry was in fact a Horcrux, meaning that he would eventually have to die. Now, as firmly established, Snape was not the greatest fan of Harry, but that didn't mean that he ever stopped loving Lily.
“Oh, Harry, James actually regretted bullying Snape a lot. He always wanted to apologize.”
However, if there is one aspect that is surprising - but also likely - is that James Potter was also jealous, bitter, and resentful of Snape. These feelings, like Snape's towards James, also likely drove James to bully, harass, and mock Snape, more so than anyone else.
Some might argue that Snape did it to play the part of a merciless teacher and pretended to hate Harry for having killed Voldemort, so he would not come under suspicion of being allied with Dumbledore. But it's pretty clear that he treated Harry like dirt to get revenge on James.
You can't make him a saint: he was vindictive & bullying. You can't make him a devil: he died to save the wizarding world," Rowling tweeted.
A Professor at Hogwarts School of Witchcraft and Wizardry, Snape is hostile to Harry due to his resemblance to his father James Potter, who bullied Snape during their time together at Hogwarts.
The simple answer: She didn't love him. The more complicated answer: He proved again and again that he wasn't willing to listen to Lily, respect her or her views, or love her in a healthy way.
We are shown that Snape hated James a lot more than Sirius. And the reason is both alluded to then told explicitly to be jealousy.
If Lily had chosen Severus, she wouldn't have defied and escaped Lord Voldemort(thrice), then Voldemort would have been left with one choice... Neville Longbottom, the child of parents who have defied Lord Voldemort thrice and who was born on closing day of July, and have the powers which Voldy had not...
Snape's obsessive love for Lily fed his equally obsessive hatred for James, and meant he would stop at nothing ' even arranging the murder of her child ' to possess Lily. Voldemort tried to spare Lily, and may have agreed with Snape, before the attack took place, to let her live.
Speaking of Lily, James doesn't treat her any better than he does Snape, he constantly harasses her and stalks her every chance he gets. James mentally abused Lily by threatening to hex her when she stands up for Snape to him, saying this abhorrent quote: "Ah, Evans. Don't make me hex you."
And although she was one of the few people at Hogwarts who was entirely unimpressed by him, her fellow Gryffindor James Potter was also deeply infatuated with her as well. Obviously Lily ultimately chose James Potter over Severus Snape, and Lily and James got married and had their only child, Harry Potter.
Her conscious refusal and readiness to die seals the charm and, thus, Harry's fate as the Boy Who Lived. Although James has the same intention of saving his family while knowing that he is likely to be killed, he is not granted an alternative for his sacrifice to put Lily and Harry under magical protection.