Being a necromancer in and of itself is going to cause some pretty negative faction.
The old answer, used to be gnomes. It might still be.
Another option might be a froggie. I rolled up a necro froglok not too long ago, and as I remember, he had okay faction in a lot of places that I didn't expect him to.
You can always just create the race you're curious about, and use pok to run to all the cities, to see if the guards kill you.
Pre-level 10, there's no death penalty.
Also, if you feel like spending ALOT of time on it, you could always just go with what you like, and repair your faction.
Plus, you don't need to visit every town in the game with just one character. That's the beauty of having alts.
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That aside, from what I understand, the least hated player race in the game isn't on Norrath at all. It's the Vah Shir on Luclin. (But they can't be Necros.)
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Maurna <The Dark Arrow Legion>
41 Warlock <Undead> - Twisting Nether
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Baron
Bellam Dreamguard of Brell Serilis (Cazic Thule) <Retired>
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"I will not be stamped, filed, numbered, briefed, or debriefed. I am a man, not a number!"