Looks around for ape slayer...
He and T rex are quests. You get a reward. You don't do damage until you get the quest. Both are lowest in cold and Energy resist. Perfect for a Cu.
Great Ape actually seems weakest to Fire damage, especially with debuffs. Usually i'll pair my Sampire/Wammy along with my Disco/Tamer, and between 120 Disco+Corpse Skin+Onslaught, i lower the Great Ape down to 4-7% Fire Resist.
My Sampire uses a 100% Fire Double Axe with 50% Lightning/50% HLA/81% HML/50% HSL/45% DI (i also use this on Chief Paroxy) which hits the Ape for 300+ total a Double Strike. My Disco/Tamer will use a 120 Chiv+AI 100% Fire Crimson Drake that deals 200+ damage a hit during EoO with all the debuffs rolling. His AI actually deals less damage than his auto attacks against the Great Ape, so Armor Pierce would've been a better option then.
Both wear Luck Suits and use the Luck Sculpture, and have 3k+ Luck after Suit+Sculpture+Honor. Can pull some good Talismans and Legendary Artifacts off of the Great Ape with that. He also drops some ML Ingredients and even rare colored Parrots, such as hue 1165. The Great Ape is basically the only decent source of high end Talismans, since all the other Talisman droppers are either Peerlesses that you have to key for with a garbage loot table (so pulling a 30/30 off of them is extremely rare), or are limited time event mobs such as the Titan bosses during the town invasions (those had good Talisman drops). The quests flat out suck for good Talismans.