being able to see that info is game dependent, with that said I don't know of any place in PDZ where you can check that info.
good luck 100%ing all your games. I see you've already 100%ed PG3 which is one of the more difficult ones, DOA4 is probably the hardest if not damn near impossible.
If I had to rank the top 4 most difficult games to get Achievments in in:
1. DOA4 <-particularly difficult because of the suvival and online achievments
2. PDZ <-particularly difficult because of the "Dark Agent" and the huge number of online achievments
3. Kameo <-particularly difficult because of the "A Rank" level achievments
4. PGR3 <- particularly difficult because of the Platinum trophys, style racer, and online pro achievments
I base that completely on how many people I've seen who've 100%ed them. With a big 0 for DOA4 and only 1 or 2 for PDZ and Kameo
Full Auto comes out soon and the achievments for that look very challenging too.
The easiest games to get achievments in:
1. NHL 2K6 <- I've heard you can 100% it in one or two matchs
2. NBA 2K6 <- same as above
3. Madden 06 <- play a few games out of a season, and sim the rest
4. King Kong <- Beat the game, it takes under 6 hours.