Monet and Vergo - They haven't miraculously turned up alive yet. They could really be dead, thus cannot be used as evidence of Oda not killing characters who should have died. More importantly, no one would care among the core cast of characters. They were pretty evil, so they weren't mourned within the story or by readers. Oda didn't explicitly show them to be dead. It was sort of assumed based on the injuries they would have sustained. No emotional closure because they were pretty terrible people. Oda didn't really hang on their deaths.
Mr. 9 - Death was maybe assumed? If we were meant to believe he was dead, there was absolutely no attention paid to him in the story. He was a minor one arc villain whose fate was inconsequential
Bon Clay - Death was never assumed; Fate was left uncertain,which in fiction, almost never means death; Most fans did not believe he was dead. His sacrifice was meaningful, but readers were not lead to believe he was certainly dead
Sabo - Same as Bon, his death was meaningful to Ace and Luffy, but Oda heavily implied Sabo was alive one chapter after his 'death', so readers were never lead to believe he was dead. Characters in the story thought he was dead for a long time, but Oda winked to the readers and let them know Sabo was alive immediately.
Pound - We didn't see him die and his dying without ever reuniting with Chiffon and Lola is not really typical of Oda's writing style; I can't speak for everyone, but I assumed he was alive based solely on the fact that, because Lola and Chiffon did not know him as their father, his death would have zero emotional impact within the story. It would be tragic from the reader perspective, but not to characters within the story. Because Chiffon didn't know him, he wasn't mourned at all and his death wasn't acknowledged.
Pell - No impact emotionally on the Straw Hats. All the impact was felt by Vivi and she learned of his survival within 10 chapters of his 'death'
Igaram - Oda wouldn't put that blood on Robin's hands; No definitive explanation is given, but in light of the fact that Robin is a good person, it seems highly plausible that there was never any real attempt made to kill Igaram. He didn't miraculously survive. His would be murderer had no intent to kill. At least that seems like a pretty natural assumption.
Pagaya - Survived miraculously, yes. His death was kind of a bit sad, but he turned up alive just when his daughter started to mourn his loss, which Oda played for laughs. His death wasn't exactly an emotional gut punch for the characters within the story aside from Conis and really wasn't the catalyst for any major character growth or story moments.
Bellamy - 'Died' as a villain off-panel. It was always a little ambiguous. He was a villain, so readers weren't invested in his character. It had no emotional impact on readers or main characters within the story.
Compared to:
Yasuie - Straw Hats witnessed his death first hand. His death was a major emotional blow and was a catalyst to major plot developments in Wano. Characters in the story believe he's dead. Readers believe he's dead.
Pedro - Straw Hats witnessed his death first hand. His will was passed on to Carrot before his death. He had an emotional farewell. His death was a catalyst for major plot developments and character growth. He was mourned and was given emotional closure for the characters. Characters in the story believe he's dead. Readers believe he's dead.
Ace and Whitebeard also fall into this category.
Oda has reversed deaths 'miraculously' in the past, yes, but usually for minor characters whose deaths were relatively inconsequential.Pedro dying is much more similar to Yasuie, Ace, and Whitebeard in terms of its magnitude and emotional resonance.
It's not that Oda avoids writing death entirely. When he writes a death, it has a direct purpose in the story to catalyze development of the story or growth / change for a character. Pedro dying fits that bill in away most others listed here do not.
