-Estimated achievement difficulty: 7/10
-Approximate amount of time to 1000: 20-25 Hours for 850, Indefinite for 1000
-Minimum number of playthroughs: 1 (As well as Fight now/Online)
-Number of missable achievements: 7 (The Champ Is Here, The Latest and the Greatest, From Chump To Champ:, Movin' On Up, Undefeated, GOAT, Big Gloves to Fill)
-Do cheat codes disable achievements?: No cheats
-Does difficulty affect achievements?: Yes (Not in career mode, though)
-Glitchy achievements: None
-Unobtainable achievements: 3 Possibly (XXL, XL, L)
-Extra equipment needed?: None
Welcome to Fight Night Round 4! First, i would like to explain a few things from the above roadmap. The amount of time to obtain the full gamerscore from this game is a tricky subject, as there are 3 achievements that are somewhat hard and rare to obtain. For the majority of the gamerscore, you will need around 20-25 hours to complete career mode and all of the singular 'Fight Now' fights, with only a relatively small amount of online play. The remaining gamerscore is obtained for 3 specific achievements, that are for beating the current online champion in 3 separate weight classes. There can only be 1 person in the world who can hold the belts at any 1 time, so you would have to find them and beat them. There really isn't an estimate on how long this would take, it would depend on your success in finding them and then their willingness to fight you.
There are 7 missable achievements, that are all career mode related. These are generally for career performance and fulfilling certain criteria in which to retire your fighter. Please consult the achievement guide for more detailed instructions.
The 3 achievements that i have flagged as possibly unobtainable are the 3 aforementioned online achievements for acquiring the championship belts. These could be considered unobtainable, due to the difficulty in finding the person who currently holds them and whether they would even be willing to part with them. Because of this fact, i have flagged them as possibly unobtainable.
Step 1: Career
Your first step should be to play through the games career mode, making sure to keep consulting the achievement guide to avoid missing any of the few missable achievements. You can play the career mode on amateur difficulty and not miss any achievements, as difficulty does not affect the career mode.
Step 2: Fight Now
The Majority of the achievements from this game are earned through 'Fight Now' which is a game mode, where you can pick your own fighter and the opponents fighter and fight them on any difficulty. There are 6 achievements for beating certain fighters on a particular difficulty. These can be quite tricky, but patience and persistence will net you these, without too much trouble. Besides beating these 6 opponents, the remaining achievements that are obtained through 'Fight Now' mode are for fulfilling a certain criteria within the fight. You can unlock these on any difficulty with any fighter, so make sure to choose your fighters wisely and make these achievements easy to obtain.
Step 3: Online
There are only 7 online achievements to earn from this game, 4 of which can be very easily boosted. You can attempt them without a boosting partner as they aren't particularly difficult, but with a boosting partner, you could earn these 4 achievements very quickly. The remaining 3 achievements are the already mentioned achievements for beating the current online champion and acquiring their belt. This could take anywhere from a few hours of being extremely lucky and finding the current retainer of the belts to weeks or even months without being able to find them, or even if the current holder would be willing to part with them.
So there you have it. A solid boxing game, that you will enjoy on your way to unlocking as many achievements as possible. Good luck with trying to obtain the online championship belts, you will need it.