Refusal of entry name removal

It all depends on why he was deported and blacklisted.
A shortish overstay is one thing but a long overstay or any criminal activity is a different matter.

It was a scooter accident causing death and he was sentenced to jail for 15 days and was held for 2months in jail prior to sentencing.

A prison sentence is normally an automatic ban and may be difficult to overturn.
Killing some poor sod will be viewed very seriously, thus your attempts are likely to be less than welcome by all the wrong people.

Further, depending on who he killed and how much malice the family hold, returning to Bali could have other dangers such as being beaten to death.

Nah there wasn't any malice at all, we became friends with the family as the other person hit my partner and passed away because he had no helmet on, my partner was also lucky to be alive and was in hospital for a while and needs ongoing treatment .

Immigration told us it was 6month ban cause he was charged with dangerous driving that's all.

Our Indonesia lawyers are writing a letter to get the name taken off the blacklist so will see.

A lot of foreigners ride motorbikes illegally in Bali as they have no licence (and are commonly drunk).
They tend to get away with it as long as they don't hurt anyone or are involved in a smash.
The other note being Australians in Bali have a less than good reputation so a lot of people aren't going to be very interested in helping out.
You might get him off but there is likely to be resistance from a lot of people.

"Our Indonesia lawyers are writing a letter to get the name taken off the blacklist so will see."

That's the best channel to use, so why bother a visa agent with this?