It took about 2 hours but i read all of the 27 pages of this post! Cant believe i made it out alive! lol
Some of the toughest bosses I fought were the Navis in Megaman Battle Networks 2. They are already hard but if you want HubStyle (which is a pain to get and when you have it you dont care anymore cause there is nothing else todo) you have to beat them with a Rank S! Thank you for savestates!
On a similar note, Rockman Zero inHARD Mode is quite impossible. The first boss was easy the first time around but now he destroys you inless than 20 seconds. Help!