- Estimated achievement difficulty: 8/10
- Offline: 40 
- Online: 0
- Approximate amount of time to 1000 : 30-60 Hours Depending on Skill
- Minimum number of playthroughs needed: 2
- Number of missable achievements: 0
- Unobtainable/glitched achievements: None!
- Cheats disable achievements: No for the Body Surf Cheat. No other discovered.
- Does difficulty affect achievements: Yes, for "Revenge Revisited"
[PROTOTYPE] is an open world sandbox game developed by Radical Entertainment and published by Activision. You play the role of Alex Mercer, a person who wakes up on a morgue slab with no recollection of how he got there, but he has extremely powerful abilities. His goal is to find out who made him the way he is and get his revenge on them.
There are no online modes in [PROTOTYPE], so there are no online achievements. However, you will find yourself getting frustrated while you grind the event achievements attempting to get Platinum medals on them.
So lets start getting those achievements! The first thing you want to do is start a Medium Playthrough.
Step 1 - Medium Playthrough - Set Up:
"Revenge Revisited" requires you to beat the game on Hard difficulty, but before you can even unlock Hard, you must complete the game on Normal, NOT EASY! In this playthrough, you will be getting the majority of the achievements for the game, but also you will be keeping an eye in how you play for two achievements: "Nice Guy" and "Hard To Kill" combined together they score 100.
For "Nice Guy" you must complete the game while consuming 10 civilians or fewer. To avoid consuming them, try to avoid picking them up with and hitting afterward - that's a consume. It's pretty simple, but also frustrating, to do. "Hard To Kill" requires you to complete the game without dying. Fans of Bioshock will remember the Brass Balls method where whenever you die, quit to the main menu and re-load your last save / auto-save so it doesn't register as a kill. Save often during this playthrough, as you'll need to restart quite often if you're new to the game.
Step 2 - Medium Playthrough:
The only achievement you won't get during this playthrough, should be completing the game on Hard, "Revenge Revisited". Everything else can be achieved in this playthrough.
My advice to get the above to achievements (as mentioned in the set up) easily and quickly is to go straight for the storyline. There are only 31 missions and they shouldn't take too long to finish. When you have those out the way, work towards your other achievements listed in the guide, which include grinding kills on Infected, destroying vehicles, shooting down helicopters, consuming targets, doing events with highest scores possible, etc.
Step 3 - Hard Playthrough:
Rejoice, you can die and you can consume whoever you want. Hard is exactly what it says on the tin, Hard. This won't be an easy ride, but as before, go for the 31 missions and nothing else. After you finish Hard, you can delete the save and go back to your medium playthough so you can:
Step 4 - Mop Up:
No doubt by now you've been playing the game for a while, possibly broken a few controllers and ripped your hair out several times. Grinding for killing the infected will take a while but is not difficult. The actual difficult achievements which give this game an 8/10 for difficulty are the Events. You need to finish them all with Platinum for the "Au" and "Pt" achievements and there are 53.
When going for them, you can find the requirements for Gold and Platinum here.
There are also Collectibles in Prototype. There are three achievements for getting all Hint and Landmark Collectibles, and for consuming all Web Targets. When going for these, I strongly suggest using these maps.
All I can say is good luck, and if there are any you're stuck on, feel free to post in the forums where somebody will be happy to assist you.