There is no tea with the most tannic acid because tea does not contain tannic acid. Tea contains tannins which are commonly confused with tannic acid, and black tea contains the most tannins.
Tannic acid is made from one specific tannin, but it is not a tannin that is found in tea. Tannins found in tea are thearubigins. Black tea contains the most tannins, which makes black tea darker than other teas. However, not all dark teas are dark because of tannins.
Tannins found in tea have both positive and negative impacts on health. A positive impact comes from the fact that tannins are antioxidants. A negative effect is tannins are also anti-nutrients which can make it difficult for the body to absorb nutrients.