The most common thought bubble with a red "x" over it tends to be when a Sim is using the bathroom, the other Sims in the household are inconvenienced because they can't use the facilities.
Some ghost Sims have this thought bubble for children on the lot if their widow/widower has remarried and has another child with the new spouse. I think the ghost Sim resents that it is not their child and it should have been. :(
Real anger and fury is displayed with the Sim in a "fire" filled thought bubble - if you play Pleasantview, there are plenty of examples due to the cheating that goes on. A Sim will take revenge and steal newspapers, kick the dustbin and maybe even fight.