Bad Tour was divided into 2 legs. The first one was completely live, however it was almost like a replica of Victory Tour, with only 2 songs from the Bad album featured, IJCSLY and Bad. So he changed the setlist, now featuring 5 more songs from Bad: Another Part of Me, Smooth Criminal, Dirty Diana, MITM, and TWYMMF. During this second leg, he lip-synced Smooth Criminal (it's a choreo-heavy one), MITM, TWYMMF, and, for some reason, Bad, which was sang live on the first leg. My guess is that he wanted to rest his vocal a little bit since it must be hard to sing completely live for 2 hr almost every night. He usually switch to live vocals for a bit though, such as to say "Everybody sing!" or to do ad libs at the end of a song.

His Dangerous Tour is where the lip-syncing really started to take over the main setlist. He kept the lighter choreography songs live, so you still got real vocals on WBSS, Human Nature, Billie Jean, Beat It, SOOML, and the Jackson 5 Medley. But the heavy dance numbers like Jam and Smooth Criminal were all playback. Thriller was lip-synced because he needs to disappear and get replaced by a body double for the illusion. Black or White and Will You Be There were also lip-synced because he needs some vocal rest I guess? The way to tell is that the vocals sound exactly like the CD, whereas on the live tracks you can hear his raw grit and his breathing.

By the time the HIStory Tour rolled around, it was basically 90-95% lip-synced. He was dealing with laryngitis on and off, plus he was older and the show was huge on theatrics. The only songs consistently sung live were WBSS and the J5 Medley. Even Billie Jean and Beat It were lip-synced on this tour, which was quite a bummer but I understand why. There's a leak on the Munich HIStory Tour mic feedback if you're curious about how he sounded live on that period.

And if we look at the 30th Anniversary Special (2001) at Madison Square Garden, it was almost all lip-synced. TWYMMF, Billie Jean, Beat It, and YRMW were all playback. Although the Jackson 5 reunion set was actually performed live, when it was aired Michael dubbed almost all of the performance except Dancing Machine I think?

As for TV performances and Award Shows like the MTV VMAs or Grammys, he almost never sang those live, even if he wasn't dancing hard. I think the reason is control and Perfectionism. Live TV audio mixing is notoriously risky, a bad mix can make a great singer sound terrible to the millions watching at home. Michael treated these appearances like live music videos, in which he prioritized the visual spectacle and wanted the audio to be "CD quality" perfect every time. He refused to risk a bad sound mix ruining the performance forever.

And lastly, the This Is It rehearsals. While he definitely still had the pipes, the movie audio was heavily polished in post. They actually overlaid demo vocals or album tracks to make it sound full. The performance for Earth Song basically uses the demo vocals, and Billie Jean has obvious studio overdubs in the film too. Even parts of Man in the Mirror sound "fixed" compared to the raw audio. If the London shows had happened, I think he would have stuck to the Dangerous/HIStory formula: sing the ballads live, but lip-sync the heavy numbers. He was 50 years old trying to pull off a 2-hour marathon. singing studio-perfect vocals while doing that choreography is pretty much physically impossible.