Nami

Makes Varus and absolute monster in lane, can trade very well, can follow up on his ulty with 2 extremely powerful cc spells, can peel, heal and buff autoattacks and also buff his movement. I consider this synergy Varus's best one.

Braum

Braum is really good against other engage supports and provides Varus with safety, peeling and cc. Don't pick him against poke mages because he will suffer.

Thresh

Provides enough cc and peeling as well as W for safety. Don't pick him against Zyra because he will suffer.

Tahm Kench

Tahm Kench is really nice against compositions that like to come into you or engage on you, He can save Varus from extremely deadly situations. Don't pick him against poke mages because he will suffer.

Zyra

Taric

A best of both worlds. A tanky cc support with keeping the carry alive capabilities. His R is really effective in teamfights since it can make Varus step up without any threat of getting oneshot, while his other spells boosts his defenses and follow up on his cc which makes Taric a really neat support.

Xerath

Bard

Lulu

Not quite as good as Lulu Kog or Lulu Twitch but she still boosts his on hit damage quite a bit but doesn't really have good kill pressure in lane.

Janna

Extremely passive supports suck with Varus and do not provide him with anything in lane where he is really good at. Janna can still poke, but she has no way to follow up on his stuff and gain leads.

Sona

Extremely passive supports suck with Varus and do not provide him with anything in lane where he is really good at.