- Estimated achievement difficulty: 8/10
- Offline: 12 
- Online: 0
- Approximate amount of time to 200: 3-10 hours
- Minimum number of playthroughs needed: 2
- Number of missable achievements: None
- Glitched achievements: None
- Do cheat codes disable achievements: No Cheats
Aegis Wing is a side-scrolling shooter, similar to Gradius and Defender. It's a fairly short game, but is still a fairly challenging 200. Most of the achievements in the game aren't challenging, but you will have trouble with "Ace". What makes this game challenging at first is the amount of enemies that are thrown at you, and you have to be able to dodge the attacks. Learning how to dodge takes time and practice, and is necessary if you want the full 200.
Step #1: Practice
Aegis Wing is challenging, so you want to start off on normal, and get the hang of dodging atttacks. Do a playthrough of the game, and try to get some of the random achievements along the way, like "Immortal", or Diplomat.
Step #2: Insane Playthrough
Insane is a huge step up from normal, with even more enemies thrown at you, and you don't get any extra lives. If you even want to stand a chance, you are going to want to play co-op. Getting a 4 player game is the most efficient, and easiest way to get through. Also, if you haven't gotten them already, you can get "Epic Warrior" and "Teamwork" as well.
To save on time, you only need to beat the final level of the game on Insane to get "Legend", but the other levels are good practice.
Step #3: Ace
The last achievement you will need is "Ace", with good reason, as it's very hard to get. Depending on your skill levels, you could play the game on normal or insane. If your already skilled at the game, you could play on normal by yourself and get the achievement that way. If however, you still have trouble with this game, you will have no choice but to attempt this on Insane, as there will not be enough enemies on normal.
There are several strategies that you can use, and one of the best ways to do it is get a second controller/player to attach onto. Have one person focus on piloting the both of you and getting the Lambda Shield, while you focus on killing as many enemies as you can. Starting from the very beginning of the game, follow this strategy, and keep practicing if you have trouble staying alive.
If for whatever reason, you still need help getting the achievement, you could always try recruiting a few extra players to act as insurance. If at any point you die, they can focus on bringing you back.
Aegis Wing is a very fun game, and seeing as it is free in the North American Marketplace, is worth your time. The only problem is "Ace", which requires patience and a bit of practice, but you should be able to do it.
[XBA would like to thank Asian47 for this Roadmap]