Little Surprised to see Giratina-O of all things being retested into OU. As i player that has wanted to see previous bans retested (within logical reasoning), I just didn't expect it to be Giratina. Where do i start, honestly i think this thing is a little too much for OU. Defensively, its typing is unique to say the least. It has a handful of useful resistances, like Water, Grass, Fire, Electric, Bug and Poison, Not to mention Immunities to Fighting and Normal Types, and a Ground Immunity is always nice (aside from Mold Breakers). Not to mention 150/100/100 Defenses (no recovery does suck though). This thing easily can fulfill a blanket check for a lot of common OU mons (Lando-I, Keldeo, Zard-Y,) Its weaknesses are still there though, Weaknesses to Dark, Fairy, Ghost, Dragon and Ice, all relatively common attacking types, but ill get to that. Offensively, 120/120 is amazing, and while the point has been bought up that it is restricted to holding the Griseous Orb, this isn't the worst thing in the world. A 1.2 Boost to its STAB Moves, which i should mention, Ghost and Dragon are arguably the two best types offensively in the game. Dark Weakness is at worst Knock Off, so any weak non-stab Knock Off won't really bother this guy. Dark Types that might give him trouble i can think of are Tyranitar and Bisharp, who can be crippled by Wisp (or Aura Sphere on the switch if you're real). Ghost weakness is pretty irrelevnt seeing as gengar is the only ghost type, and he takes a ton of Damage from Shadow Sneak. Dragons if they are faster, but still fear switching into a Draco or Dragon Claw/Tail. Ice Types can get bopped by Aura Sphere so they still have to be weary of switching in. Fairies i do admit might give him some trouble, but Faries are easily checked and can be handled. The next point i would bring up are the move sets it can run. Honestly, you could run dual Stabs and have two support moves like wisp, defog, destiny bond, roar, rest, thunder wave, toxic and tailwind, all viable support moves, so its a pretty big guessing game at what it can run. If you want a more Offensive approach, you can run CM with D-Pulse/Shadow Sneak/Aura Sphere which has Perfect Neutral coverage. Overall, i admit that Giratina has its flaws (Easily Checked due to its low speed, Common weaknesses, Pursuit weakness) but i don't think thats enough to viably say that i feel comfortable letting this thing back in OU.