Adjective
simultaneous - Refers to actions or events that are performed or experienced at the same time, without any time between them.
They made a simultaneous broadcast of the event across multiple time zones that allowed people from all over the world to watch it live.
unforgiving - Not making an allowance for error or weakness in others; not willing to forgive others for things they might have done wrong.
Because they knew that Alaska in the winter is an unforgiving environment, they had to plan their expedition very carefully.