What line from act iii of hamlet supports the conclusion that claudius fears his own fate?

"What if this cursed hand

Were thicker than itself with brother's blood

Is there not rain enough in the sweet heavens

To wash it white as snow?"

In this excerpt, we can see that Claudius fears his own fate. He confesses to the murder of his brother ("with brother's blood"), and realizes that this makes him a cursed man ("this cursed hand"). He also wonders if there is something in the world that could possibly help him redeem himself ("Is there not rain enough in the sweet heavens/To wash it white as snow?"). He desires to be cleansed of his sin, but believes it impossible, which worries him greatly.

roses are red,

violets are black,

for what you said,

i hope you sit on a big fat tack.