Well if you want hard go for Thug/Illusion it is so evil 
It will make any one cry when it pops gang war.
Well the hardest would be Dark/Ninjitsu.
The funnest IMO would be Ice/Fire Troller primaries with both pets unlocked.
I made ss/reg with rage he can hit through high def, so not a cake walk for /sr, aand since he has regen, thats an av with dp, MoG, and IH. Not very funny when he revives though.
Willpower has more passive regen than Regen does. Who thought that was a good idea?
Can we get a fix for Energy Melee instead of more new sets?
Mind Control/Stone Armor is painfully hard, Especially if you are a mastermind!
Mass Confusion for the lose.
Anything with above "Standard" level Regeneration is very, very hard. Dual Blades is painfully weak. My non IO Scrapper build (he's Willpower) could AFK and not die... DB was on "Extreme" too.
[Anything]/Stone Armor is not fun, even if they do not have Granite. Oh, I tried Energy Blast/Mental Manip., both extreme. He wasn't bad until he popped Drain Psyche
DB does seem weak. On the other hand SS/BS/WM/MA are really hard hitters. Rage+KO Blow+ Footstomp =dead player toon if those two hit, which they do even through soft capped defense with relative ease.
The development team and this community deserved better than this from NC Soft. Best wishes on your search.
Be careful with Blaster Fire as a primary. Super Reflexes I had to replace because lower-damage teams didn't have a prayer on one.
#28470 - MA & YOU! Quick Tutorial
Poster 1481: Cause of How Some Silly Stealed My Wings
Cultist fun in 3586 Project: Perilous - Into the Chthonian Pit
Formerly of Perils of Paula!
I haven't tested it, but DB by itself IS kind of weak if you don't do the combos. I'm wondering if the AI is set up for combos.
Dec out.
Electric Assault/Electric Armor can be a real pain with the end drain.
Virtue: The-Invictus (Blue)
The Emissary of Justice - Level 50 Fire/Fire Blaster
The Emissary of Justice. - Level 50 WP/Fire Tanker
Mesmerius - Level 50 Psi/Mental Blaster
Nucleoa - Level 50 Rad/Son Defender
What are some fun custom AV's you guys have come up with, the more challenging the better.
@Nova King