Liabilities of Quesh is a Galactic Seasons objective in SWTOR. You must kill two Imperial and two Republic bosses to complete the Objective. Every Champion can easily be killed as a Solo player using a Healing Companion.
As Quesh is a level 36-37 planet, you may want to complete the Seasons Objective on a level 37 character.

Liabilities of Nar Shaddaa is a Galactic Seasons objective in SWTOR. You must kill two Imperial and two Republic bosses to complete the Objective. Every Champion can easily be killed as a Solo player using a Healing Companion.
As Nar Shaddaa is a level 19-24 planet, you may want to complete the Seasons Objective on a level 24+ character.

Liabilities of Corellia is a Galactic Seasons objective in SWTOR. You must kill two Imperial and two Republic bosses to complete the Objective. Every Champion can easily be killed as a Solo player using a Healing Companion.
As Corellia is a level 46-50 planet, you may want to complete the Seasons Objective on a level 50 character.