Some nasty code to inject pickles with (almost) arbitrary code
from nasty_pickle import patch_pickle_bytes
def my_bomb():
print('kek')
pickle_payload = ...
payload_that_will_print_kek_on_unpickling = patch_pickle_bytes(pickle_payload, my_bomb)
my_bomb can contain any code that is convertible to oneliner, so no ifs, loops, exception handling and so on.
And don't forget to include necessary imports