Chlorine is the element with highest electron affinity.
Even though fluorine is the element with most electronegativity, because of its small size, it experiences more repulsion when adding one more electron to attain stable electronic configuration.
Chlorine on the other hand with considerably larger size can accommodate an electron easily . So, it has more electron affinity than fluorine.
Short answer: Chlorine has the highest electron affinity on the periodic table.
