I have to disagree, PPAULO.
Vindictive and Vengeful means vingativo(a).
Rancorous means rancoroso(a).
Resentful means ressentido(a).
Although these words are related to each other, the meanings are different.
A vengeful person is rancorous or resentful without a doubt.
However, some people does not show their feelings and keep them inside, suffering alone.
These are the resentful. They don't know how to took revenge on the ones who made them suffer; or they just want to avoid fights, living with fear. Some even forget what happened but they keep the bad impression of the bulliers, for example, and forget what was the reason who made them to become vengeful. It is a serious mental disorder which can make them to develop different personalities or commit suicide if not treated correctly.
Not all resentful people are vengeful.
A vengeful person needs to do something, in fact, to be called that way.
A rancorous just defines someone who holds or have grudge.
Hard feelings represents all of negative feelings we hold, but not all of them are related to a revenge directly.
Hard feelings is not only revenge. It can be sadness, sorrow and bitterness too.
A sorrow represents a mix of disgust, regret, bitterness and sadness. It is difficult to precise them, after all we are talking about feelings here.
Although a sorrow is often mild, it can leave traces that can last for a long time. Sometimes it is possible to perceive it in a person's countenance, words, gestures.
(1) Pearson Education. Longman Dictionary. 2004.
(2) BRAIN, Christine. Advanced psychology: applications, issues and perspectives. Cheltenham: Nelson Thornes. 2002.
(3) MCCULLOUGH, Michael. Beyond Revenge : The Evolution of the Forgiveness Instinct. Jossey-Bass. 2008.