Someone who is feckless is incompetent and lacks the determination or skill to achieve much of anything at all in life.
When you are listless, you lack energy and interest and are unwilling to exert any effort.
A hapless person is unlucky, so much so that a stream of unfortunate things have happened and continue to happen to them.
When someone speaks in an artless fashion, they are without deception; when someone acts artlessly, they are being totally natural.
A fruitless endeavor does not bring about a successful result; rather, it has been time spent pointlessly.
Someone who is ruthless shows no pity or mercy at all to an opponent.
If you do something that is senseless, there is no purpose or good reason behind doing it, and the thing that's done is often harmful or stupid in some way.
If someone does something that is pointless, there is no reason behind or meaning for doing it.
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