AP Varus
I am not saying it is better than AD, but these two builds have done good things for me. Both destroy tanks. This full build does more damage than the adc Varus build. (tested in sandbox mode)
or
situational
So if you are interested in trying this keep this in mind. It is not strong at all early game. The on hit one is okayyyy early but Luden's first is slow. You could throw in
instead. The goal is to maximize DPS. Three auto attacks then your ult is max damage, but of course that is not always up. His W works well with his abilities. If you did not know when you hit a champ with an ability the ability consumes the blight stacks for max HP %. The more blight the more max % they lose. THIS HAS AP SCALING!!!!! In theory 3 basic attacks and any ability on a champ will take them to under 50% hp no matter how much HP they have.
Spacing and knowing when to attack the enemy is key. Hurricane lets you stack blight on multiple champs then your E will nuke them. Gunblade is good for the healing and slow you get from it. It will help you land combos. Liandry's adds additional % damage and burn to your initial damage.
Only play this is normal game please until you get the hang of it. It is a very unique way of playing Varus. Treat him like Anivia. Do not do anything but farm until you know you have the damage to fight. Once you get the hang of this build it is very rewarding though. No one on the enemy team will expect the damage. One full stack ult on the other team's engage is all you need to win a team fight. This build late game will easily one shot adc's unless you get outplayed. The most reliable best combo seems to be: aa, R, aa, aa, Q, aa, E(so they cannot run) if they are not dead here you did something wrong.