

This may come as a surprise and I don't really get it myself. Obviously I can use Kyurem in White 2 after I get Reshiram and beat the main story. Grinded it a to max out mainly speed and special attack, but not extensively.
Regular Kyurem could not kill much and was surprisingly worn down quickly. Mostly because I used Glaciate for style points. In the White Treehallow during Area 9 onwards I decided to use White Kyurem. I can't count the number of times it failed to 1HKO something even with Freeze Burn. Maybe the moves I used weren't that good: Dragon Pulse, Ice Beam, Fusion Flare, Freeze Burn.
Something is missing and I feel like it is the same issue with Reshiram and Zekrom in BW after you obtain them. They are maybe useful only against the first Pokemon N uses and after that they get owned by anything. Post Game Pokemon destroy them because either too bulky or too fast and strong. White Kyurem suffered similary but it was trained obtaining some evs.
Helpless against Cynthia and most strong Pokemon in the tree. I don't think it will be useful in the Pokemon League either. Last time I checked the stats, it had 300 Special Attack around lv 75.
It does deal massive damage on Super Effective hits I guess. Most of my in-game team members just outperform it with lesser stats like Magnezone, Excadrill, Braviary or Zoroark. Not sure where the real issue lies. Nature is Gentle so it is not getting a Special Attack Drop.