Macadamia Nuts
A cup of Macadamia Nuts pack the most calories. Macadamia Nuts itself contains 718 cal per 100 grams.
Explanation:
A cup of Macadamia nuts contains nearly 950 calories (1/2 of a person average calories need). The cup contain 132 grams of calories filled nuts. But, the standard size of serving is about 1 oz which contains about 204 calories.
(screenshot taken from myfooddata.com)