Linus Pauling is indeed the only individual to have won two unshared Nobel Prizes - the Nobel Prize in Chemistry (1954) for his work on chemical bonds and the Nobel Peace Prize (1962) for his nuclear disarmament activism.
Linus Pauling is unique in having won two unshared Nobel Prizes: the Chemistry prize in 1954 for his work on chemical bonding, and the Nobel Peace Prize in 1962 for his campaign against nuclear weapons testing. No other individual has won two Nobels alone in different categories.