>>718369824 (OP)
>63 crit Rutger
If you aren't close to 100, you're playing handicapping yourself by not utilizing Rutger's supports. That's what makes him truly unstoppable.
Swordmaster + Killing Edge = 30 + 30 = 60
His absolute minimum skill is 12 on normal and 13 on hard (although you want to get him with 15 skill from hard mode bonuses), with the +2 from promo that puts him at 14. Skill is divided in half and added to crit in FE6, so that's +7.
We're at 67 crit right there, assuming zero skill level ups, which is unlikely but not impossible. The big boost missing comes from support. Rutger has the darkness affinity, so any A support gives him 7.5 crit, and any support besides Dayan's (he has the anima affinity) will also have the crit bonus, yielding 15 extra crit from an A support. With a B support, you can get an additional 10, for 25 total from supports.
So:
7 + 30 + 30 + 15 + 10 = 92 crit before subtracting luck
On hard mode, Maggie can have 11 crit maximum, so the absolute worst case scenario with a B and A support available would be 81 crit. WORST CASE SCENARIO! Rutger has a 60% skill growth, so it's actually really easy to see him hit 100 crit with supports. That's the power of friendship.