The sink drain pipe was changed to ABS (previously metal), but it leaks at the point where it joins the drain in the wall.
Teflon tape was added on the ABS pipe where the washer contacts it (and possibly on the wall drain pipe threads, but I'm not sure). Then some kind of epoxy was applied on the the wall drain pipe and over the nut. It still leaks (badly).
How to fix this mess?
EDIT: I chiseled off the epoxy and removed the ABS pipe. Now it's clear the nipple, if that's what it is, is severely corroded (see image below) and is most likely the cause of the leak.
How do I remove the nipple, which is really solidly stuck and seems like it will easily get crushed? A Youtube video suggested carefully cutting a tab into the top of the nipple and squeezing it into an oval shape to "easily" unscrew and remove it. Recommended?
Also, assuming I get the nipple out... what should I replace it with? Another galvanized steel nipple or something else?