No Challenger 2 has been destroyed because not many Challenger 2 tanks exist, and not many have seen combat. Fewer than 500 units have been built for the armies of Britain and Oman, not more than three British regiments (battalions) have been equipped at one time with them, and their only combat service was perhaps one battalion in Basra, Iraq.
Compare that to more than 10,000 Abrams tanks, with extensive combat exposure in Afghanistan and Iraq, over 1000 Merkava 3 and 4, also with a lot of combat exposure in Gaza and Lebanon, and over 3000 Leopard 2s serving in many armies, without as much combat exposure but considerably more than Challenger 2, having served in Afghanistan and Syria.
The Wiki page on Challenger 2 notes one survived several RPG hits plus a Milan ATGM, and another survived an IED. That’s impressive, but Abrams, Merkava, and Leopards have done the same. Some Abrams and Merkavas have survived multiple heavy Russian ATGM hits from Kornet and Metis missiles. All have survived IED detonations, just like the Challenger 2 in Iraq.
By this standard, one might say that the French Leclerc is better than the American, Israeli, and German tanks, too, since in its small combat exposure—in Yemen with Yemeni forces—none has been destroyed either, but that would be pretty silly.
The difference is risk exposure. The few Challengers that operated in Basra were not exposed to as much combat or as intense as the other tanks. Eventually, if enough missiles hit enough tanks, some will be destroyed. Same with IEDs. In the case of the US, Israeli and German tanks, that has happened. In the case of the Challenger, it did not, and given the small number in service with the British, probably never will.
All these tanks are comparable and so far have proved as much when exposed to significant combat.