I know some of the French tanks had pretty poor guns as far as tank-killing went - low-velocity 45mm - as they were designed for infantry fire support (eg. R35; the R40 version was upgraded to a better long-barrled gun), but their "line" designs like the S35 had high-velocity guns quite capable of taking on anything the Germans wielded.

And then there was the Char B1 series, which gave German tacticians well-founded nightmares long before they had to actually fight the beasts. The BEF's Matilda IIs proved to be almost as troublesome, although not quite as destructive owing to their lighter armament.

Bet you the German commanders were quite unhappy about having to fight those nasties mostly with PzKpfw IIs (which weren't actually supposed to be part of the line of battle anymore, but there wasn't yet enough IIIs and IVs to go around to phase them out) nevermind now the tiny Is, which were really training vehicles by that time.

It's not like the Panzer II was a poor tank or anything, it was just plain too light to rumble with the big boys and wasn't really meant to either. The entire "light tank" concept was really a bit flawed that way; they weren't really cost-effective. 'Course, the even smaller "tankettes" suffered from that and then some, as they didn't even have turrets to help out with the "speed is armour" thing...

Then again, arguably any AFV is better than nothing at all, if only for infantry support against MG nests and suchlike.