In Act 4, as to Fortinbras, Hamlet seeks to maintain his father's example of honesty and fairness even in times of war. Fortinbras knows no such limitations. He will sacrifice "two thousand souls and twenty thousand ducats" to have the right to territory that is virtually worthless except to say it belongs to Norway (4.4.15-30).
Speaking to Hamlet vs. Laertes, whereas Hamlet makes sure of the virtue of his deed in seeking to avenge his father (though some critics see this as his weakness; that is, wavering instead of certainty), Laertes waits for no such verification. He seeks bloody revenge against Hamlet for his father's accidental death and plots with Claudius to make it happen. He would even "cut his (Hamlet's) throat in th' church" (4.7.144). Claudius agrees that "(r)evenge should have no bound" (4.7.146) and the two plot to make it happen, one aware and the other, Laerets, his fool.