rightest

being or located on or directed toward the side of the body to the east when facing north;
free from error; especially conforming to fact or truth;
socially right or correct;
in conformance with justice or law or morality;
correct in opinion or judgment;
appropriate for a condition or purpose or occasion or a person's character, needs;
of or belonging to the political or intellectual right
in or into a satisfactory condition;
intended for the right hand;
in accord with accepted standards of usage or procedure;
having the axis perpendicular to the base;
(of the side of cloth or clothing) facing or intended to face outward;
most suitable or right for a particular purpose;
precisely accurate;

rightest is a valid Scrabble (US) TWL word

rightest is a valid Scrabble Word in Merriam-Webster MW Dictionary

rightest is a valid Scrabble Word in International Collins CSW Dictionary

rightest is a valid Words With Friends word