First time I played Normal (the first time I played the game full stop) I died fifteen times...seem to remember that the first Dr Salvador was responsible for one of these deaths, Del Lago once, that I died twice in the cabin fight, twice in the water room, once in the Garrador cage, once in the King's Grail area, twice in the two Garradors room, once from Verdugo, once from a Regenerator, once from an Iron Maiden, once in the wrecking ball room and once in the knife fight with Krauser.
Interestingly enough, the only two chapters that I have never died in (on any difficulty level full stop) are 1-2 and 4-3. Chapter 1-2 looks a little scary when you first play the game- that mountain fortress is just crawling with Ganados, but in practice it is quite an easy area. And as for 4-3, you would think that with the high Ganado count (around 70), the collapsing ceiling, the minecart ride and not to mention FOUR Dr Salvadors in the one chapter, it wouldn't be quite so easy. But I have always found it an easy chapter. Have most other people found 4-3 easy as well?
But yes I've beaten easy, normal and pro, Assignment Ada and have earned five stars with every character on all four levels in Mercenaries. Getting five stars for Leon and Hunk on Waterworld took me forever though. I wish I had access to Seperate Ways, alas I don't as I have the Gamecube version.