Mass Effect has a total of 45 achievements that can all be yours if you play through the game a minimum of 3 times, but even then you might screw yourself out of an achievement because you didn't do something you thought you were supposed to do. Mass Effect has a lot of moments like that..
Because of the decisions I made, I need to play through Mass Effect a minimum of 4 times to gain all the achievements now... I just completed it for the second time, so that leaves 2 more to go!
24 of these achievements I would class as counters.. Do this or collect this a certain amount of times and you get the achievement.
A couple of these you'll easily get on your own.. like 250 synthetic kills, 150 organic kills.. I think i'd be more difficult if you completed the game killing less than 250 synthetics.
There are 4 achievements for killing an enemy 150 with each type of gun. These are pretty easy too. Once you get one achievement, start using a different weapon. There's an achievement for using 150 medi-gels.. Not too tough.. Just lead your cohorts into the line of fire and then heal them afterward. As you continue through the game, you'll get it in no time.
These are 2 achievements for alignment. If you reach 75% paragon, you get an achievement and the same with renegade. Gamefaqs has a few glitches to earn infinite paragon and infinite renegade, but I couldn't get them to work. It's pretty easy to tell which conversation options will get your paragon and renegade, but throughout the game there isn't enough to get both achievements in one play through. You'll need to get one on the first playthrough, one on the second. If you're achievement-whoring this game, this is no big deal.
The real pain are those pesky "use this ability 75 times" achievements of which they are 11 for a mere 15 points each. It's pretty easy to get in the habit of using your abilities, but those Tech abilities are not too useful in battle. I really don't know what the point of these achievements are.. What do we really achieve by using these abilities 75 times? If anybody has more than 6 or 7 of these achievements, you can tell they have a lot of time on their hands.. They take absolutely no skill to achieve.. Just time and consistency.
I have no idea if you get the achievement if instruct your party member to do the ability the 75 times, or if your character has to be the one to do it. I will probably test this out in my third playthrough.
Lets see.. 2, 6, 7, 9, 20.. one of the remaining 4 is getting 1,000,000 space credits. This is not a challenge what-so-ever. Just be an item-whore, which is standard for RPGs (getting all items everywhere), and selling off the ones you don't need. You'll reach 1,000,000 way before the end of your first play through. In fact, it didn't take too long in my second playthrough to hit the max of 99,999,999 credits and 999 omni-gels.
Another 2 counter-based achievements are for experience. You get an achievements when you reach level 50 and level 60. You should be able to hit level 50 in your first playthrough if you do absolutely everything. Hint: You gain twice the amount of experience if you kill enemies outside of your lunar rover. Well, more accurately, killing things with the lunar rover will cut the gained experience more than half.. At the end of my first play through, I was 6,000 xp away from level 50.
Getting to level 60 is a royal pain. You need 860,000 experience points to get level 60 and at the end of my second playthrough on New Game+, I ended around 750,000.. So i'll need to do another New Game+ with the same character i've been playing for 50 hours now to hit the 60th level.
You need to complete one playthrough before unlocking levels 51 through 60.
The final collection-based achievement is "Scholar", which is finding all the main Codec entries for the main alien races of the Mass Effect Universe.
You can get this achievement before you leave the citadel the first time, but you can screw yourself by not asking the right questions.. Before Eden Prime, ask Captain Anderson about the Protheans, and right after Eden Prime, ask Anderson about the Geth. Those are the only two entries you can miss. The other ones you can get by talking with Avina terminals, the Hanar in the Presidium Emporium, the Elcor in his embassy and the Volus dude in the Elcor embassy. Once you're a spectre, talk to Anderson about the Batarians. That should do it.
There's a full list in this faq: http://www.gamefaqs.com/console/xbox360/file/930279/50960. Search for [SCH].
17 of Mass Effects' achievements I would consider progression based... meaning, you get an achievement when you beat a level or progress through the game.
You cannot beat the game without getting 7 of these, but the other 3 are more sidequest related. "Completing the game a second time" and "Landing on an Uncharted world" are self explanatory.
The one side-quest achievement I missed on my first playthrough was the romantic subplot, which is pretty easy to get.. I was looking in the wrong place. Just like real life.. :/
The romantic subplot involves you (the main charcter) and one of two party members. If you're male, you can get it on with Ashley or Liara. If you're female, you can sex up Kaidan or Liara. Be sure to talk with the teammate you're hot for after each main mission, and you'll be in bed with them right before or after Ilos.
Completing 75% of the primary assignments and 75% of the secondary assignments will net you the main achievement, but there are 6 other achievements for each party member. You must have them in your party at the time of completing that quest for it to count. So be prepared for the Long haul.
Getting the achievement for Ashley and Kaidan is quite easy since you have them in your party from the start. You get Garrus in your party pretty early too. Wrex and Tali aren't too bad, but you'll need to put them in your party right away and never switch them out.
Liara is the most difficult to achieve. You'll need to ignore all the sidequests in the citadel and go to Artemis Tau immediately after becoming a Spectre. Once completed, head back to the citadel and complete all those sidequests are go from there.
I really had no idea how to get these achievements, so after two playthroughs, I only have 3 out of 6. On my next playthrough, I'll probably go for Wrex and Liara since I've been playing with the same people for both games and I need a break.
There are 4 achievements that require actual skill.
"Complete Mass Effect on Hard" and "Complete Mass Effect on Insane". The gamefaqs guide says to get these achievements you must select your difficulty in the options before you start a new game. However, I was able to get the Hardcore achievement by switching my game from Normal to Hard as soon as was able to after starting a New Game +.
I got this one without any trouble, so you probably don't need to worry about it. I'm guessing the description is self explanatory: The total amount of damage you sustain will be absorbed by your shields MORE than one your person.
The description reads "resolve an impossible situation with charm or intimidation". Basically, level up your charm or intimidation based on your alignment and there are 2 instances I know of where you must choose all the charm or all the intimidation conversation options. These 2 times are: on Virmire when Wrex gets all pissed off about killing Krogan, and at the end of the game when you face Saren.
Personally, I have 29 out of these 45 achievements. I like playing Mass Effect quite a bit so I'll probably go through at least once more, but some of these achievements are really a waste of time. I just need to reach level 60 with my current character, then i'll start over with a male character and a new class finally.
Also, I think my addition is off a little bit on the above numbers..
Sources have been this Gamefaq, Gamefaqs in general, and personal experience.