"I love pineapple on my pizza."
Translation:J'adore l'ananas sur ma pizza.
When you use verbs of preference, likes and dislikes, you must use the definite article with the object. So "J'adore" + partitive article + noun is never correct. Same goes for aimer, préférer, détester, etc.
Also "du ananas" puts two distinct vowel sounds together, which is also not correct. If you must use the partitive article, it's "de l'ananas".