contentious(marked by controversy) adjective [UK: kən.ˈten.ʃəs] [US: kən.ˈten.ʃəs]The issue turned out to be very contentious. = La questione si è rivelata essere molto controversa.
controversial(arousing controversy) adjective [UK: ˌkɒn.trə.ˈvɜːʃ.l̩] [US: ˌkɑːn.trə.ˈvɝː.ʃl̩]That's very controversial. = È molto controverso.
moot(subject to discussion) adjective [UK: muːt] [US: ˈmuːt]
questionable(problematic; open to doubt or challenge) adjective [UK: ˈkwes.tʃə.nəb.l̩] [US: ˈkwes.tʃə.nəb.l̩]