Mostrar = to show/demonstrate? amar = to love? matarle = to kill him? (I forget whether it was le or se)
Matarse = to kill oneself, although to say "matar" + direct object (me/te/se/le/nos/les) pronoun, it works. You got the informal command correct (mata), but you constructed it incorrectly. You needed an accent over the first "a" in "mátate" because the emphasis of the word falls on the first syllable (as in
yo mato) even though it isn't as fluid -- see also
this under "Imperativo".
Personally, I would have preferred
... y tambien todo el mundo le molesta Joe (Joe repulses all of the world, or literally, Joe molests all of the world) to "no ama a Joe" (you forgot the "a" for a verb's direct action to a person).
