I need an eeveelution for my team, but I don't know which one. I heard flareon was awful and sylveon was good, but I just don't know.
Edit: Stupid autocorrect made "flare on" and "sylvan". I fixed that.
Based on the two Pokemon you have here sylveon seems like a good choice. Both your absol and lucario are weak to to fighting type attacks which sylveon resist in addtion lucario covers both sylveons weaknesses quite well being immune to it's poison weakness and resisting it's steal weakness. Also sylveon resist absol's bug weakness. The nice type synergy and it's great bulk on the special defense side as well as it's respectable special attack and access to pixelate boosted hyper voice makes sylveon a great choice.
