Whey concentrate protein is the most complete, highest quality protein on the market today. When it’s grass-fed and combined with digestive enzymes, such as in Metabolic Fuel, even those with dairy sensitivity are likely in the clear.
If you must go with an alternative, pea protein is the second best option, but it is not a complete source of all essential amino acids. Hemp protein is a complete plant-based protein. Soy protein should never be used.