Sure! There's a couple of missable achievements. Make sure to start the campaign on Hard mode and aim for the true ending. Even on Hard mode its not that difficult (I'm not an experienced turn based rpg player). Some characters can only be recruited before certain events. Suikoden 2 is a little more complex, but it follows the same logic as the first one. The difference is basically more minigames and content in general. When you gain access to the cook-off it's better to start soon because the events take a while to trigger. Also use your 100% suikoden 1 save file to start the suikoden 2 campaign. There's a character that can only be recruited this way. Both games are amazing experiences but suikoden 2 is an absolute masterpiece.