The correct option is
C Blessing
The word 'catastrophe' refers to something very unfortunate or unsuccessful.
Option A, beneficial refers to something that results in good, favourable or advantageous outcomes.
Option B, blessing refers to a beneficial thing for which one is grateful.
Option C, soothing refers to something that has a gently calming effect.
Option D, disastrous refers to something that can cause great damage.
Thus, according to the meaning, the word 'blessing' is the most different in meaning from the word 'catastrophe'.