Certainly, ISU-152 became greatly feared by German heavy tank crews. Like on 14 March 1945 in Hungary, twentyfour dug-in ISU-152 (protected by a minefield) managed to damage sixteen Tiger II from schwere Panzer-Abteilung 509. Later during the day, two sPz.Abt 509 Tiger II seized the strongpoint, knocking out all twentyfour "beast killers". After five days, all battle damaged Tiger II were repaired and running again. Ironically, only 10 days later, fourteen of these Tigers II had to be destroyed due to lack of fuel (source: Wolfgang Schneider: Tigers in Combat)
Indeed they were and to such an extent that they falsely claimed those. I hope you don't think of me as a necromancer, but I had doubts about that encounter initially, and
this blog post I came across recently reinforced my suspitions even further, so I deciced to conduct my own investigation on the matter.
The only units in the area between Velencefürdő and Tükröspuszta (according to
this map, original
here) armed with ISU-152s were 1443th SPA Regiment of 23th Tanks Corps (6 vehicles) and 363 Guards SPA Regiment of 18th Tanks Corps (4 vehicles, 3 operational) with
only 4 ISU-122s lost during the period from 13th to 15th March. Well, maybe then Germans then had mistaken ISUs for some other type of SPAG? The only relatively closest engagement in terms of Soviet losses I could find occurred on 12th March when
60 German tanks attacked positions of 207th SPA Brigade, disabling 19 out of 63 SU-100 it had in expense of their own 38 tanks and SPGs.
That means that either Soviet (which I highly doubt) or German battle reports are incorrect,
which is not surpising taking into account the mess in German papers towards the end of the war and the fact that many of them were simply lost.
EDIT: Added picture to comply with the rules:
The grave of French tankers and Char B1-bis tank near Châlons-sur-Marne.