Call this a challenge?
Easy. A top-level conjuror with all his cash blown on scrolls of Gate.
Round 1: If the tarrasque wins Initiative, your Contingency is triggered and you get Teleported out of reach. You then Maze the tarrasque (no save, no SR)
Round 2+: Quickened Haste, then gate gate gate
Repeat until tarrasque returns.
Send in umpteen solars and dispatch him.
Alternately, top-level cleric with Spell Penetration and the Magic Domain: he has used scrolls to cast Haste, Improved Invisibility, Mirror Image and Contingency: Teleport. And an absurd amount of Blade Barriers scrolls, and a few Wall of Force scrolls.
Round 1: Tarrasque attacks, contingency triggered (as standard)
Round 2: Cast Maze from scroll (or Forcecage etc.).
Rounds 3-5: Erect Walls of Force with the scrolls around where the tarrasque will return. Six placed cunningly should do the trick.
Round 6-X: Cast all Blade Barriers inside the Walls of Force (remember to allow gaps so that YOU can get past the WoF but the tarrasque cannot.
When the tarrasque returns, he will fail SR against roughly half your blade barriers, and even if he makes his save, cannot move out of the affected area. In subsequent rounds he will have to continue making saves. If worst comes to worst, renew the Walls of Force with more scrolls. When the tarrasque has been suitably sliced into shreds, cast Miracle.