Here's how Gemini says Muhammad Ali does vs Tyson's 10 title defenses from 86-90

Here is how Muhammad Ali would have handled the men Mike Tyson defended his crown against:
1. James "Bonecrusher" Smith (March 1987)
Tyson's Reality: Smith fought defensively, tying Tyson up constantly to survive a 12-round unanimous decision.
Ali's Matchup: Smith was big, strong, and possessed a devastating left hook, but he was notoriously gun-shy when pressured. A prime Ali would have completely played with Smith from the outside, circling away from that left hook, snapping a piston-like jab in his face, and winning a wide, lopsided decision or late-round TKO.

2. Pinklon Thomas (May 1987)
Tyson's Reality: Thomas had a phenomenal jab, but Tyson broke him down and stopped him in the 6th.
Ali's Matchup: Thomas was a skilled boxer-puncher with a great jab, which makes this a fascinating technical battle. However, Ali's hand speed, footwork, and volume from angles would have overwhelmed Thomas. Ali wins a clear decision or a late technical knockout.

3. Tony Tucker (August 1987)
Tyson's Reality: Tucker was an undefeated, tall, slick boxer who fought Tyson with a broken hand and managed to take him the 12-round distance.
Ali's Matchup: Tucker had the right style to give problems—good size, decent movement, and a solid right hand. But Ali was simply faster, sharper, and possessed superior endurance. Ali would out-jab and out-maneuver Tucker over 15 rounds, though Tucker's toughness likely carries him to the final bell.

4. Tyrell Biggs (October 1987)
Tyson's Reality: Biggs was an Olympic gold medalist with beautiful amateur skills, but Tyson mentally and physically dismantled him before stopping him in the 7th.
Ali's Matchup: Biggs tried to use lateral movement against Tyson, but didn't have the power or chin to keep him off. Ali invented heavyweight lateral movement. Against a prime Ali, Biggs would find himself completely outclassed in a masterclass of footwork and speed. Ali by wide decision or late stoppage.

5. Larry Holmes (January 1988)
Tyson's Reality: A retired, shopworn Holmes came off the couch on short notice and got brutally knocked out in the 4th.
Ali's Matchup: This is the ultimate "Passing of the Torch" fantasy. If you put a prime 1960s Ali against a prime 1978–1980s Larry Holmes, you get arguably the greatest technical heavyweight fight in history. Holmes actually learned his legendary jab by sparring a young Ali. Ali wins a razor-thin, highly strategic 15-round decision, though Holmes's brilliant left hand would make it a war.

6. Tony Tubbs (March 1988)
Tyson's Reality: Tubbs was a highly skilled, slick boxer-puncher, but Tyson caught him and stopped him in the 2nd.
Ali's Matchup: Tubbs had fast hands and great defensive instincts for a heavyweight. He would have given Ali a competitive first few rounds, but Ali's work rate, psychological dominance, and championship stamina would take over down the stretch for a clear decision win.

7. Michael Spinks (June 1988)
Tyson's Reality: Spinks was an undefeated lineal champion who was utterly terrified of Tyson and got blasted out in 91 seconds.
Ali's Matchup: Spinks was a brilliant light-heavyweight great moving up, but his style relied on awkward angles and psychological disruption. Ali dealt with awkward, unorthodox fighters (like Cleveland Williams or Karl Mildenberger) with ease. Ali's speed and reach would completely neutralize Spinks, leading to a clear, dominant decision.

8. Frank Bruno (February 1989)
Tyson's Reality: Bruno stunned Tyson briefly with a jab, but succumbed to Tyson's pressure in the 5th round.
Ali's Matchup: Bruno was physically imposing and had a concussive jab, but he was notoriously stiff, upright, and prone to fatigue. Ali would have picked Bruno apart from the outside, landing crisp combinations whenever Bruno dropped his hands. Ali by mid-to-late round TKO.

9. Carl Williams (July 1989)
Tyson's Reality: "The Truth" Williams was a smooth boxer with a great jab who caught Tyson with a good shot early, but got flattened in 93 seconds.
Ali's Matchup: Williams gave Larry Holmes a hell of a tough fight. However, Ali's footwork and hand speed would prove too much. Williams might catch Ali with a stray jab, but Ali's superior combinations would secure a clear decision or stoppage.

10. James "Buster" Douglas (February 1990)
Tyson's Reality: Douglas fought the fight of his life, utilizing a stiff jab, lateral movement, and a right hand over the top to shock the world and knock Tyson out.
Ali's Matchup: Douglas fought with a specific blueprint: tall, rangy, throwing a fast double-jab, and refusing to be intimidated. Ironically, this is the exact style that historically gave Ali the most trouble (think Ken Norton or Jimmy Young). A peak Ali would still adjust and likely win a tough, competitive decision, but a focused, peak-motivation Buster Douglas fighting like he did that night in Tokyo would give any version of Ali a grueling night.

The Verdict
While Tyson destroyed his challengers through sheer, terrifying velocity and destructive power, a prime Muhammad Ali would have swept Tyson's entire catalog of challengers primarily by out-boxing, out-speeding, and frustrating them.

I tend to agree. Ali might more decisively win the Holmes one, but I doubt he stops him and it goes to the cards.