What are the main character's first words in Hamlet? What do they tell us about him?

Hamlet's first words appear in Act 1.2, line 65.  The
line is:

A
little more than kin, and less than
kind.

Delivered as an aside,
or spoken directly to and only to the audience, the line uses puns to ridicule Claudius,
who has just referred to Hamlet as his kinsman (cousin) and his son.  Kinsman is used
for relatives outside of one's immediate family, and son, is of course,
son.

Hamlet plays on these two terms in his
response. 

When Hamlet says that Claudius is more than kin,
he is saying that Claudius is too much of a relative, both uncle and stepfather:  the
stepfather part is too much.

When Hamlet says that Claudius
is less than kind, he is saying the
following:

• Claudius is unkind for taking the
  throne from Hamlet, the former king's son and rightful
  heir.


• Claudius is unkind, of a certain kind, an unnatural
  kind, because he has married the wife of a dead brother, which is considered incest in
  Shakespeare's time and within the play.

Hamlet
is sharp, witty, and definitely unhappy about his uncle's marrying his mother and
claiming the Danish throne.  Hamlet doesn't yet suspect Claudius of murder, since this
scene appears before Hamlet's meeting with the Ghost.  But he certainly does not
consider himself to be the new king's son.