Furious First ResponderG 55

To earn the Achievement, you need to do:

Paramedic:
level 12 in one go

You should complete this Paramedic mission at the beginning of the game, before attempting any missions in Portland. The hostiles will grow more aggressive as the game progresses. This level becomes harder when they start shooting at your vehicle. It takes about 15 to 20 minutes to finish.
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The others are quite easy because they accumulate, so you can do them in multiple attempts.

Vigilante
20 on Portland
20 on Staunton Island
20 on Shoreside vale

Firefighter
20 on Portland
20 on Staunton Island
20 on Shoreside vale

On Shoreside Vale, I found a glitch with the fire truck. Just stay on the street where the phone box icon is, and the burning cars will keep reappearing on the same street, back and forth.