3.5 was edition I played the most. It was a reason why I quit RPGs for nearly a decade because I hated it so much.
Every time I see another meme about how amazing 3.5 Tarrasque is, I remmember how amogn actual 3.5 players Tarrasque was the biggest joke. It was always brought up as definite proof designers have no idea how to make good monster. It was laughably easy to beat. A wizard could casually solo it, the same abilities people now miss in 3.5 amounted to ribbons. It was a laughingstock, forums had 100+ pages discussions how to fix it and general consensus was it';s beyond saving. It was first proof in 3.5 if you cannot use magic you're only good to roll over and die.
I honestly don't know if everyone claiming 3.5 Tarrasque is such a horrifying monster are trying to rewrite history or unintentionally proving what a broken, unplayable pile of garbage 3.5 was, if it's biggest punching bag is actually dangerous in a different, better designed game.
I've been thinking it would be cool to have a campaign set after the town has gotten smaller. You go on your first mission to fight a cave full of kobolds or some such, there's an earthquake that blocks the exist, and you have to fight through it and escape before later tremors cause it to cave in. It's fairly standard, until you leave, and find out what was causing the tremors. At some point decades or even centuries ago, the rate they dealt damage to the tarrasque dropped below the rate it regenerates. Then it spent all that time slowly losing the nonlethal damage, until finally it was enough to regain consciousness. The city is left in ruins, and now the nations of the world have to deal with the tarrasque acting like a roving natural disaster. Maybe at the end, you have a choice to rebuild Salt in the Wound and get that source of alchemical supplies back, or kill it for good as the only way to be sure this never happens again.