Drow are a culturally evil society, but that obviously means that some drow aren't evil.
Shar worshippers are worshipping an evil deity by choice and thus are almost certainly evil.
Angels are (Lawful) Good essentially by definition. If they change alignment then they turn into a fiend (or other creature depending on alignment), unless I'm mistaken (e.g., Asmodeus, Zariel).
Undead...are typically evil, either because they're mindless (and try to kill people), because being evil is a prerequisite for becoming undead (lich), or because undeath corrupts your morals/thoughts until you're evil (vampire). It's interesting that WotC removed the Undead creature types from the Reborn and Dhampir lineages -> one reason they might've done this is to preserve player alignment freedom, which then implies that undead are required to be evil.
