Answer:

severest

Answer	Crossword Clue
SEVEREST	Most austere
SEVEREST	Extreme to the extreme
SEVEREST	Strict to the extreme

SEVEREST	Most rigid
SEVEREST	Most rigorous.
SEVEREST	A kind of critic.
SEVEREST	"Dearest friend, ... critic."
SEVEREST	Most keen.
SEVEREST	Harshest.
SEVEREST	Gravest
SEVEREST	Most harsh

Crossword

a puzzle consisting of a grid of squares and blanks into which words crossing vertically and horizontally are written according to clues.