Can I use Reuniclus' "Damage Swap" ability to move all of my damage counters onto one Pokemon and then knock it out?
You can only move one damage counter at a time with Damage Swap (even though you can re-use the ability many times), so as soon as the number of damage counters on the Pokemon equals its HP, it would be KO'd immediately. In other words, you cannot move ten damage counters onto a Pokemon with only 50 HP and then knock it out.
Source: Black & White FAQ (2011-04-28), PUI Rules Team (2011-04-28)