I understand it was heavily fictionalized, but 300: Rise of an Empire depicts Artemisia as pursuing a personal vendetta against the Greeks for murdering her family and keeping her captive; thus she influenced Xerxes towards war. Xerxes, in turn, also presumably wanted revenge on his father's death.
So, is there anything similar in actual history? Someone plotting vengeance on another nation for many years, before making into a position of power and carrying out their plan?
By and large, within dictatorships and monarchies MANY conflicts arise due to personal slights of honor and the holding of grudges. The Wars of the Roses is a good example, as it really just boils down for power-grabbing within the branches of one family tree.
Xerxes hatred of Greece was specifically a grudge against the Athenians. In the years before 300 would have taken place, a group of Greeks living on the outskirts of the Persian Empire in Ionia realized the Persians were moving in on them and sent for aid from mainland Greece (this being a big deal because mostly Greeks were straight on each other and were essentially at constant war with each other, making it unlikely that anyone would do anything). The city of Athens sent a token force, mostly intended as a show of force, not as a actual attempt to draw battle, and things got out of hand. The in-flux of men lead to a lot of rabble-rousing and somehow fighting began and a Persian port city was burned to the ground. Thus the Persians began to eye the Greeks for vengeance and eventual conquering because they'd already meddled in Persian affairs.
Kings of Germany and the Papacy had beef for a long time which lead to a lot of conflict.
Really, when you have one family/one person in power, many of the conflicts end up being personal in nature. Plus the reasons for conflict can never be entirely put onto one single issue, and usually the reasons given to the public are not the real reasons, and its all a big mess.
Short story...yes. Almost constantly.