To unlock Lobo you are required to have access to Apokolips.
Once you have completed the main story mission on top of Lex Corps you can gain access.
Once you have gained access to Apokolips you are required to complete the following.:
1. Break up the throne in darkseids throne room.
2. Collect the purple stud which is over the lava area.
3. Complete the gold brick missions, and the character quests.
4. Once you have done these you will then unlock the Lobo quest
5. Attack the goons on the way to the Throne room then take 3 selfies with him to unlock him.
Now you can unlock Lobo
by purchasing him for 150,000 studs.
As soon as he is purchased pop achievement unlocked 50g richer.