His two most strongest Pokemon are easily his Bisharp and Krookodile able to do severe damage. The Elite Four of Unova is made up of teams of only four, not five, Unova-exclusive Pokemon at first, each Pokemon having great emphasis on strategy and counters to your own team making it quite the challenge and all the more rewarding once you defeat them.
Personally, I think the hardest and most balanced Elite Four easily has to be 5th generation's take and is also a great example of why 5th generation Pokemon are one of the greatest list of Pokemon out there.
What do you think were the Hardest and Easiest Elite Fours ever created? I've noticed there aren't many Pokemon Polls that talks about this and the ones that do talk about it are either very outdated or they are not only outdated but have very outdated polls locked to Generation 4 or below.