Unthoughtful
Part of speech: adjective
Definition: inconsiderate of other's feelings unplanned or unthinking
Thoughtless
Part of speech: adjective
Definition: Marked by or showing lack of due thought or care; careless.Inconsiderate, inattentive.Lacking thought or consideration.
Example sentence: Most times, Mother Earth's resources are used up without the realisation that these thoughtless actions might just be the root cause for the hardships future generations may face. It is everyone's responsibility to hand over a green, clean, and healthy environment to them.