TV shows sometimes convey incorrect concepts and messages. One of a very serious one is this:
"人不為己，天誅地滅"
One will see this line from any characters in any TV shows who done something selfish and maybe hurted others.
He/she will said this to justify what he/she had done.
Under such cases, this phrase means "If you are not selfish, God will punish you!"
But, don't be misled like all Hongkongers, true meaning of it is actually "One has to keep improving himself, physically and spiritually, or else God will punish him!"
Original saying in whole is :
"人生為己，天經地義。人不為己，天誅地滅"
Hope you get the meaning behind!