If you are determined to use Venusaur as a sweeper then you absolutely need a Talonflame check. Heatran is the first who comes to mind as it benefits from the sun but Rotom-W comes to mind as well as having two fire pokemon may feel redundant and Rotom-W can also offer much utility in volt switch and thunder wave. Just my two cents.
Tyranitar also deals with talonflame pretty well and the sand helps to reset charY's sun