Cockatrice

Flying
Whenever Cockatrice blocks or becomes blocked by a non-Wall creature, destroy that creature at end of combat.

30th Anniversary Edition

Time Spiral Timeshifted

Fifth Edition

Flying
If Cockatrice blocks or is blocked by any non-Wall creature, destroy that creature at end of combat.

Fourth Edition Foreign Black Border

The ability destroys the creature at the end of the combat, which is after all first strike and normal damage dealing is done. This means that a creature may have to regenerate twice to survive the combat, once from damage and once again at end of combat.