>>75708Neutral, probably.
"Fucking up" isn't as easy as it sounds, when it comes to alignment, so long as you're consistently in character, you're probably remaining true to your alignment.
See, I play Sister Ash as Neutral Good. I try to keep her intentions genuine, and try not to make her perform any acts that may seem needlessly malevolent. She follows reasonable laws out of courtesy and politeness, but she doesn't regard the laws of ponies as any sort of binding authority that comes close to the righteousness of morality, so she may act independently of good.
Were I to suddenly make her needlessly greedy, malevolent or sadistic for no real reason, that would constitute as "fucking up", because it's not in-line with her sense of morality thus far.
As a Druid, I can only be Nuetral, Neutral Good, Lawful Neutral, Chaotic Neutral, or Neutral Evil. If I switched to a prohibited alignment, I would lose my class abilities.
Being Neutral Good also means that there are some spells on my list that I cannot cast. I cannot summon Salamanders, since they are Evil Creatures, and thus conjuring them is an evil act. I cannot cast Contagion since that's a spell with the Evil subtype in its descriptor. Sister Ash may never cast Spells that create or control undead, even if she gained them through special feats or other classes.
I cannot take Feats such as Child of Winter or Nightbringer's initiate, since those feats require the character to be non-good.
If I had the Planar Shepard prestige class, I may not dedicate myself to any plane that was even mildly evil aligned.
Fighters have no alignment based restrictions that I can think of, unless you're thinking of a particular prestige class. Divine casters are the main classes to have alignment restrictions, since their power comes from their religion. If you have certain feats or prestige classes that have alignment based restrictions, those may be a thing, but I don't know about them.