Use one list as search key for another list with sublist of list

[jc4d]

I tried disecting it but is not taking me far since eventhough it is returning the difference, the result is not "filling back" to what list it belongs, which should return
['pear', [-1, 2, 3]]

list1 = [['orange', [1, 2, 3]]]
list2 = [['apple', [1, 2, 3]], ['banana', [1, 2, 3]], ['pear', [-1, 2, 3]], ['kiwi', [1, -2, 3]]]

S = set(tuple(x[1]) for x in list1)

a = [x[1][0] for x in list1]

b = [x[1][0] for x in list2]

z = [x for x in b if x not in a]
print(z)