Images (1., 2., 3., 4., from El humor otro, 1963):
(1. "at noon the shadow hides under the man";
2., 3.): very simple figures convey a Leopardi type of humor;
4. Sa-Lo-Mon builds his own prison to escape afterwards using his imagination (more complex ideas were deemed too obscure to Fidel);
5. Chago Armada's painting Lo amorfo y descorazonador del diálogo vacío (the amorphous and disheartening of vacuous dialog), 1968: some of Chago's abstract paintings and drawings are clearly influenced by his comics, but not in a Neo-Dada, detached, ironical, "I'm an alchemist transforming lead into gold", kind of way. There is a very direct, very creative vein between the two (in these multi-tiered paintings with speech balloons I wonder if there's any difference). Until proven wrong I suppose that Chago Armada created abstract comics.
PS On second thought, maybe Lettriste extraordinaire Isidore Isou is also a contender.