how about the british "achilles" version of the m10 tank destroyer? the introduction of the brits' more powerful anti-tank gun defined this destroyer in the same way that the up-gunned firefly 'defined' the sherman.
now please don't hit me for saying anything against the beloved sherman[:0]
, but until it got its new gun, it lacked effectiveness against a lot of german armour unless employed in overwhelming numbers (which it usually was, i know, but that's not the point i'm making...).
just my view from this side of the pond....
regards,
nick