Who considered killing Gollum but took pity on him instead?

A.

Isildur

B.

Bilbo

C.

Elrond

D.

Sauron

B. Bilbo. Because, after Bilbo took the ring, his first thought was to kill Gollum but after he heard him crying thief and crying for his "precious" [which was actually a "birthday present" from his close relative (He strangled him for it) ], he was sorry for him and decided not to.

Fun Fact!: Smeagol (Gollum) was actually a hobbit at first, and lived a lot longer than any hobbit could!