Any support can be a "damage" support with artificial numbers. Spellblade, Echo, Gunblade, Fire Cape, Thornmail, et cetera.
Many supports weren't even designed with "supporting" in mind. Look at Blitzcrank for example: 3 obscene AP scalings, an AD-multiplier and an AS booster. Literally his only "defensive" tool is his mana-shield passive.
Not to mention how many countless mid-laners have become meta support picks: Morg, Brand, Zyra, Malz, Vel and even Syndra & Lissandra for short moments.
Hell, I once had a support Lucian that did really well, because I didn't want a fucking useless-ass Sona on my team. As far as I'm concerned, this game has 138 viable support options, about to be 139 once Zoe is released.