Inhumanely is the adverb of inhumane: in a very cruel way, causing pain that people say is too much. The pattern you will meet most is treated inhumanely — animals, prisoners, workers. You can also punish someone inhumanely, or keep them inhumanely. It is a strong, serious word, more at home in news and in law than at the dinner table. It is simply inhumane plus -ly. Though actually, some speakers say inhumanely and inhumanly as if they were the same. Teachers like to keep inhumanely for cruel treatment, and inhumanly for “not in a human way” (a machine moving inhumanly). In real life those two also mix.