Alistar

You can follow up her engages with R and he can peel for you very good

Amumu

Amumu can peel very good and also engage so you can follow up with R. He's pretty much a better Alistar

Annie

Boring to play with her. Just play nothing laning phase and she will carry your team lategame

Ashe

Just poke with her together with your Q and play a safe lane

Bard

You can trade with him together well and he scales with you

Blitzcrank

After level 6 you can follow up on his hook with your R. Before that your follow up isn't huge

Brand

Braum

You can help him proc his stun good and he has amazing peel for you

Janna

You can follow up on her knock-up and she scales hard

Karma

Deals so much damage early game, while still scaling good

Leona

Very good All-in and peel

Lulu

You can trade very good with her together and she can R you if you get in trouble

Lux

Poke out the enemy with her together. After level 6, if she lands a Q you can both Ult for a guaranteed kill

Milio

His W helps you a lot in extended fights. Furthermore, his damage in early trades and shielding late game is insane

Morgana

She can be a good counterpick against Supports like Blitzcrank, but Varus synergises better with other poke-supports

Nami

Very good trades and All-ins with her R

Nautilus

Fine synergie, but Naut is better paired with other ADCs (Samira, Kaisa, etc.). Although he can peel very well

Pantheon

He has good early damage and you can follow up on his stun

Poppy

Can peel really good for you, good counterpick against a lot of dashes (Rakan, Samira, etc.)

Pyke

He can't peel for you, because he's way too squieshy. Sometimes he accidently hooks the enemy away from your R and sometimes you overkill with your damage resulting in you burning all your cooldowns, even though pyke would've gotten the kill nontheless with his ultimate

Rakan

Rakan can function as an anti-engage champ, so he has lots of peel. Still, he has good engage which you can follow up on

Rell

Good peel, good engage, can combo ults

Renata Glasc

Renata has good poke and her W combined with Varus's burst can often result in a revive which be fight-winning

Senna

You can poke with her together, if she lands a stun you can follow up, she has good disengade tool with her mist and she can heal you. Senna scales good and the only thing she's missing is peal

Seraphine

You can poke with her and she scales with you, but nothing special with this synergie

Shaco

You won't be able to follow up on his boxes (except maybe with your ult). Also, he doesn't provide a lot of peel

Sona

She will help you survive laning phase, and then scale extremly hard lategame

Soraka

She will help you survive laning phase and can trade so good, and then scale extremely hard lategame

Swain

He does a good damage early, resulting in you getting a lot of kills. Furthermore, you can ult the enemy while they're in swains ult, which is pretty much always a kill

Taric

Unlike other ADCs who fight the enemy in close range (Samira, Nilah, Kai'sa, etc.), Varus won't be able to hit the enemies with Taric's stun. Still, Taric's ult is amazing peal and you can get a lot of kills with him while still staying relatively safe

Thresh

Fine synergie, nothing special to mention

Vel'Koz

Very good poking and trading. Your ults combined also deal massive damage. But he doesn't have any heal/shield or peel for you

Xerath

You can completly poke the opponents out of lane with Xerath. Although you don't have a lot of synergie with his ult

Yuumi

Since Varus has no mobility, once you get hooked, both of you are dead. But she can enable you to carry the game late ron

Zilean

Fine synergie, nothing special to say except that he provides good peel

Zoe

If the enemie botlane is rather squieshy, you completly destroy them with this pick. Charge up your WQ while the enemy is drowsy and shoot it so that it hits right AFTER Zoe lands her Q, so you get more missing health damage. Only downside is that she often solo kills the opponents

Zyra

Good laning phase. You can combine you'r ults for huge damage