How about "redoubtable"?

Awesome: Grand, magnificent, awe-inspiring, commanding, outstanding, marvelous. Cool: Splendid, striking, intriguing, compelling, provocative, beguiling, thought-provoking, titillating, engrossing, tantalizing

'Awesome' can be used formally, but it is overused. The latest Spiderman movie was impressive. The Great Wall and the Grand Canyon are awesome. Use it sparingly. 'Cool', formally, would 'excellent' or 'first-rate'

"Most capital." The fact is, if you are looking for superlatives (formal or no), you have to be VERY careful which one you choose. You cannot shove one in place of another.