Level 5 is the maximum karma status you can reach. You may unlock this near the end of the game, but chances are you won't unlock it by doing only the story missions. This trophy is the harder out of the two, as getting good karma is harder than getting bad karma. Here is what you should do to get this trophy in the quickest time possible.
- Always choose the blue options in missions, you should be doing this anyway on your good playthrough.
- Always heal civilians on the floor.
- Always restrain enemies when they surrender, or are on the floor.
- Complete drug bust activities.
- Hit enemies in the leg with the neon power.
- Rescue civilians trapped in cages.
- Heal prisoners being attacked by mobs
Hopefully post game you should be near the end of level 4. If you are lower than that, you will need to do a lot of grinding. Just keep going around completing drug bust activities and healing civilians until you get to level 5. This shouldn't be needed though if you avoided doing evil things as much as you could on your good playthrough. Here's an additional tip to easier raise your good karma, thanks to Dougiefresh613
"When i beat the game on my second playthrough I had about three quarters of a level to go to get to Hero level. If you find a drug bust, complete it, then die, when you respawn it will pop back up again close to you on the map. It makes it much faster to farm karma, well good karma anyway."