He was against the dread masters, not one but 6. Even with help of troops. The dread masters were a force to be recon with but far from invincible. I doubt that jaric kaedan would last 1 minute against the emperor.
Him being the most powerfull jedi also debatable. But even considering that, i cant see how the dread masters are more powerfull then the emperor. wich was the point.
Yea i forgot to mention that i thought the Emperor was far stronger than the Dread Masters. They themselves admitted that the emperor was stronger than them and that only he was worthy to command them. Also theres only 1 force user that the emperor is afaid of and thats Revan, aside from him Vitiate doesnt really care about anyone else.
Of course Jaric Kaedan would lose to the Emperor, be in his prime or not. Just in his prime i think he could hold his own for a time similar to Revan, but that would be only if he could get past Vitiate's mind control which always seems to work at least on the first try.
Jaric Kaedan's probably the strongest in his prime due to having the most credntials of any other jedi of the time during the GGW. He beat the dread masters, invented the Juyo'Kos style, and was considered a living weapon of the jedi order.
Satele hasnt ever beaten any noteworthy sith (just dueled Darth Baras to a draw as a jedi master at best)
Tol Braga has dueled DC member Darth Sajar to a draw turning him to the light at best
Orgus Din lost to Darth Angral (who wasnt even on the DC)
Bela Kiwiiks lost to Lord Praven (Darth Angral's apprentice)
Wyelett beat Darth Baras but lost to his apprentice after he had become vastly more powerful from communing with the force.
Syo Bakarn hasnt beaten any noteworthy sith (albeit his other personality is about=to a DC member at best.)
Jun Seros the Jedi Battlemaster and Kellian Jarro lost to a bounty hunter.
Need i say more?