There's also something to be said about Syndrome wanting specifically to be Mr. Incredible's sidekick as a kid. Bob was a brick. He was built from the ground up to tank damage. He's the worst possible choice for Buddy to have wanted to be a sidekick to, but that didn't matter, because he was the most famous and therefore the most desirable. Syndrome probably could've offered his skills to any number of heroes who would've taken him up on it. Hell, he could've understudied under Edna Mode if being useful actually mattered to him. But he HAD to team with the best, because that's all he really cared about.
Syndrome never had a chance to be Bob's partner regardless cause he didn't want a partner. When he says "i work alone" it wasn't just telling off a kid, it was to show Bob has trust issues.
People don't get that Bob wasn't really perfect and he was a foil to syndrome in more than just power.
Bob didn't just miss the glory days, he was "addicted" to being a hero. In the flashback he is late to his own marriage. He has a room for himself where he can look at his heroic feats literally saying "glory days". He was already heroing in secret with frozone. Helen knew this and he gives a "it was just a little workout" like he's a crackhead relapsing. He takes the first opportunity he can to use the suit again, almost dies and keeps doing it behind his family back cause he doesn't care. His cheating to heroism is intentionally portrayed as cheating his marriage with another woman. He didn't want his family involved and only by the end of the movie he trusts them.
Buddy was a TRUE fan but he didn't *get* heroism, he was a dumb kid obcessed about helping ONE hero instead of helping people ("I only wanted to help you"). He was a stalker who studied all Bob's move and made his entire idendity around being his fan, which is not how any sidekick is created. Even when he talks about "being true to myself", he comes to conclusion he is "Incrediboy" cause he understands his hero, with zero grasp of the danger he is in. In fact,
his flashback is unreliable narration and doesn't even show bomb voyage. When shit goes south he thinks Bob hates him for lacking powers and that evolves into, as bob says, "killing every real hero so you could pretend to be one".
The way they end is obvious opposite and the moral lesson of the movie. Bob realizes he's not invincible, lets go the past and trusts others. Syndrome grows overconfident and fucks his own allies. Bob is saved by his wife, helped by Mirage, beats the robot with his family, and brings heroes back. Syndrome is betrayed by mirage, beaten by omnidroid (who dies to ti's own claw) and dies shortly after gloating about stealing bob's son.
It's not the greatest villain of all time but it's just a nice clean duality of being obcessed with "being hero" and using your gif for good. Syndrome works cause he was a literally a dumb kid who didn't get it. He would never work nowadays cause Disney would make him a stupid and sanitized tragic villain and miss the point.
I know this because it's what they did in Incredibles 2. The (shitty twist) villain hates heroes because... her parents died and they didn't save her while heroes were outlawed and does unironic monologues (mocked in first film) and "people rather watch than help" political commentary.