Warning: SPOILERS ahead for IT Chapter Two.
IT Chapter Two saw The Losers' Club return to defeat once and for all not only the monstrous Pennywise but also the infinitely more human threat of Henry Bowers - albeit in a drastically different manner than in the books. Bowers is a character taken straight from Stephen King's popular novel, upon which the films are based. The history between him and the saga's heroes spanned decades, with Bowers initially serving as one of King's most notorious of school bully characters. After Pennywise and The Losers' Club became mutually aware of each other, however, Bowers was driven increasingly mad by the demonic entity - all as a way of further targeting his collective nemeses. After Pennywise was seemingly defeated, he also served as a perfect cover for the former's most recent crimes.
Played by Nicholas Hamilton, Bowers was featured prominently in the first IT film. Though many were sufficiently toned down or outright cut in the transition from page-to-screen, plenty of his atrocities from the book remained. Most notably, he still engaged in racially-motivated attacks against Mike Hanlon. He also actively tortured Ben Hanscom - going as far as to actually carve the letter 'H' into his stomach. He later murdered his father at Pennywise's instruction. After the group decided to finally fight Pennywise beneath the house on Neibolt Street, Henry confronted them. With every intention to kill them, he was ultimately overcome when Mike shoved him down the house's well.
Given the sheer brutal nature of Henry's fall, audiences believed that the filmmakers had opted to write Bowers out early. When IT Chapter Two was released in theaters, however, that was proven to not be the case. Similar to the novel, Bowers was later apprehended by the police when he finally emerged from within the sewers. Convicted of the recent string of murders, he was remanded to an institute for the criminally insane. He remained in said custody for the next few decades, until Pennywise awoke and The Losers' Club returned to Derry. Guided in his escape by the former, he was entrusted with a mission to hunt down Bill, Beverly, Richie, Eddie, Ben, and Mike. In the film, Bowers is ultimately defeated once and for all when, during an attempt on Mike's life at the public library, he is killed by Richie via an ax to the head. Things, however, played out a little differently in the books, as Eddie originally killed Bowers.
The book's scene played out in largely the same manner. Mike fared much worse on the page, though, receiving a near-fatal wound during the subsequent fight. As a result, he was forced to remain at the hospital to recover while the others ventured back down into the caverns beneath Derry. In the book, it is also not Richie but Eddie, in fact, that killed Bowers and saved Mike. Eddie's weapon of choice, however, was a broken bottle. Though some may feel that Eddie was robbed, he actually still got his due. As well as successfully defending himself against Bowers a few scenes earlier, he got to fire off a perfect zinger regarding Bower's hairstyle in the process.
The reasons for the change will, of course, be known only to IT filmmakers. Still, it's not difficult to theorize why they opted for the switch. IT Chapter Two, after all, is very much an ensemble piece. Unlike the book, however, there is a limited amount of time to tell the story and give each character their due. Given that Eddie would go on to make the ultimate sacrifice to save a friend, it made sense to give Richie the earlier savior moment instead. Also, moments before, he was attempting to flee the town before thoughts of Stanley Uris forced him to turn around. As such, it also made for a logical, triumphant beat for Richie's arc at that moment and gave IT Chapter Two a cathartic, fist-pump of a moment.