Start with Rogue Scout, level 20, max Dex, increase Dex to 22 by use of Manual of Quickness of Reaction, Braces of Archery, +3 longbow, +3 arrow, arrow treated with Purple Worm Poison, shot with Advantage for Sneak Attack, roll20 or use Adamantine +3 arrow for critical hit, sharpshooter feet.
Start with Rogue Scout, level 20, max Dex, increase Dex to 22 by use of Manual of Quickness of Reaction, Braces of Archery, +3 longbow, +3 arrow, arrow treated with Purple Worm Poison, shot with Advantage for Sneak Attack, roll20 or use Adamantine +3 arrow for critical hit, sharpshooter feet.
+6 prof, +6 Dex, +3 bow, +3 arrow, gives +18 to Hit, 15 sharp shooter = +13
2d8 ,+18, +2 for braces, 10d6 for sneak, 12d6 poison, +10 Sharp Shooter = Damage = 2d8 + 22d6 +30 (min 54, max 190 average 122)
600m range, and he can do it twice in one go (has to be 2 targets)
Can this be beaten?
Never had much interest in playing Rogue, but Rogue Scout I'm going to have to try, an All Seeing Ghost Carrying a Howitzer, I can work with that :)
Dum Vivimus vivamus
Use one of your ASIs to get the Fighting Initiate feat, and select Archery, for another +2 to hit.