I just completed the game... with Raphael and only with his initial weapon (Saï) ! I can also say I didn't use any continue, and didn't abuse of pizza respawns.
I can't say I was a big player at TMNT, cos even if I discovered this game in 1990, I finished it for the first time on March 2011 ! I didn't try the game again until last week, when I thought to try and finish the game, only by using Raphael and his Saïs. In fact, I didn't think it could be possible. But after some hours of practice, I noted there is only 2-3 really difficult parts, and once you're sure of your strategy for them, the challenge isn't that hard.
Level 1 :
Very easy, so I never really try to do it properly. ^^ But here, it was pretty ok.
Level 2 :
Nothing special. As I'm not doing a speedrun, I secure some parts to dive into the river with full energy. I did 2 mistakes near the end, but I had enough health to allow them.
Level 3 :
The latest building is one of the hardest parts of the game, if not the hardest. In fact, the boss' 2nd form is the main problem, so I wanna be sure to start this battle with almost full life. I lost only an half life bar before, and it's the best I could do I guess. It's better like that cos I didn't make a very good battle here.
Level 4 :
Not very hard, but the possible instant death in Tunnel 17 is always stressful, and I was close to the death here ! ^^ And apart from a bad Tunnel 05 where I lost 4 life bars, this level was done pretty correctly.
Level 5 :
Extremely easy if the Technodrome is in the northeast hole... but it wasn't here. :'-( I had some troubles to come back as I hate the Porcupines, hopefully there is a half slice of pizza. Finally, the Technodrome was in the southeast hole. The last screen was difficult, and I wasn't really happy to start the battle against the Technodrome with 4 life bars left... Hopefully, I did one of my best fights against this boss, so it compensated.
Level 6 :
By far the level I worked the most during the practice, so I really know it by heart ! Everything works perfectly until I got the whole pizza, but just after, I accumulated the mistakes... First of all, I was pretty sure I won't see the Ostrich as I was following the Whirlybird. Normally, you can jump over the Ostrich without receiving damages, but I jump too late here and I lost 3 life bars. In the next screen, I did 2 another stupid mistakes, so I started the death row with only 3 life bars left !
At this moment, I was pretty sure I won't be able to pass it entirely, even if I knew what to do to manage it without receiving any damage ! But in a single-segment, and with the pressure, I couldn't believe it... But surprisingly, I was able to do everything perfectly and I got the miracle : no damage at all in the death row ! I was pretty happy by this, especially when the road becomes smaller, cos you need a good timing to hit the Whirlybirds twice before they hit Raphael.
After that, the last Laser Soldier and Shredder are normally a formality, but something will be wrong with Shredder. Maybe I was 1 or 2 pixels too much to the right, but Shredder didn't act as he usually does, and he finally took his gun. Hopefully, I reacted just in time and I was able to kill him with another strat. But I didn't think about an ultimate fright against Shredder ! ^^