What are some similarities and differences between the characters Hamlet, Laertes, and Fortinbras in Hamlet?

All three men try to take
revenge for fathers murdered, but each are delayed in doing so, and each
regret the act after:

Fortinbras takes
political action to avenge his father's death.  Old
Fortinbras was killed by Hamlet Sr., and Hamlet Sr. was already killed by Claudius, so
Fortinbras decides to wage war on the entire state of Denmark.  He tries to be a man of
action, but he is called back by his uncle, the sick king of Norway.  So, he wages war
on Poland instead.  In the end, when he reaches Denmark all are dead, and though his
invasion is bloodless, he never really enacts personal revenge.  He is the only avenger
standing, a lonely enterprise.

Laertes tries to take quick
and personal revenge for his father's murder, first on
Claudius.  Claudius advises that he wait and kill Hamlet during a rigged fencing match.
 After he is stabbed, he regrets his role as avenger because he has been used as a tool
for Claudius' revenge.  In the end, quick personal revenge causes one to be
manipulated.

Hamlet is caught between revenge
and mercy, mainly because of fear of damnation and problems with his
mother.  His father mandates revenge, though Hamlet is unprepared to do so.  He delays
revenge because of fear and supernatural misgivings: how to send Claudius to hell and
his father and himself to heaven (is it even possible?).  In the end, he enacts revenge
on Claudius, but it comes after he is killed.  He has lost everything: mother,
girlfriend, and his own life.