Is the vegan diet the most healthy diet in the world? or is it missing some vitamins?

Not healthy diet: Vegan diet does not include any dairy product or egg. Vitamin d supplementation is therefore mandatory.

It's deadly: There is much bad information about vegetarianism / veganism and the claim that it's incredibly healthy simply isn't true. Vegetarians don't live longer than other folks when you control for other habits, and a vegan who doesn't know exactly how to supplement always becomes B12 deficient and often runs low on iodine, iron, vitamin d, and zinc. Governments even provide guidelines for vegans.

Vegan is NG: The long term effect of a low fat, vegan diet is malnutrition. Used for a short time (4-6 weeks) a low fat diet can be employed for weight loss. However, the long lerm effects of low fat diets are miserable. A low fat - high carb diet will lead to high Insulin levels, high triglcyerides, low hdl, metabolic syndrome and finally high blood pressure, diabetes and heart disease.