There's an Oldenburg at my barn. VERY much a pissy, pissy mare. I've watched her be ridden by multiple people and she will use anything as an excuse to have an absolute fit and then sulk for hours. If she trips over a pole it's YOUR fault and she will then be mad at YOU for hours.
Very loving to humans on the ground but if she decides that she's mad at another horse and you are in-between her and them, she'll take you out to get to them. I do nightly feeding and I have to remove her first from the pasture so I won't get kicked or trampled by her as she's always mad at someone.
Her training has been very spotty the past few years (her owner was injured, then PG and then had an ill child) which hasn't helped her attitude in the slightest. She's leaving with my trainer on a 6mo lease for an advanced student of hers, so she will be in full training with constant lessons. Should be very interesting to see how her attitude is when she returns.