Just Checked and Crono has 277 health and Robo has 265... so do the math... anyway that's enough of me Defending myself (you gotta admit this is childish to fight over)...
Anyway arashi no tora, you got a point in what you said in your last message:
"Anyway... if you would fight Final Kefka at level 16, would he be hard ?
And the One Winged angel Sephiroth at level 20 ?
That must mean they are the hardest boss ever...."
so I guess that we all have to take things from Perspective.
(Warning Final Fantasy X Spoiler Ahead)
In FFX I took out my Aeons with an Overkill every hit... My Friend got killed by almost all his Aeons (thank god for the Faeyth)...
(End of Spoilers)
Especially in the Case of RPG's it just depends on Your Level and skill... also I thought the Topic was asking what each of OUR All Time Hardest Boss was... I mean it's impossible to say one boss is the Hardest over all... I mean I found DOA2's Tenchu (or whatever his name was) to be really hard... I eventually got good enough to beat him within 5 tries... so in retrospect we all need to take into consideration each others Skill.
On a side note i took on Sepiroth's Last form (well technically second to last) with No Level 4 Limit Breaks and on a very low level... can't remember exactly so i must say he was MY second hardest boss of all time... (I Survived on HP Materia alone, and of course a little skill , just if you were wondering(on another side note i got my arse whooped by him approx. 20 times in one session... took a week to finally beat him, lost count of overall defeats))