Tentacruel offers strong special defense with resistances to Fire, Water, Poison, Ice, and even deals with Grass types well. There are a few niches to mention, with respect to his insane weakness to Earthquake. Tentacruel has access to barrier and reflect, which, on a predicted counter switch, can be set up to take the edge off the shock. Substitute is another option, and eases prediction a bit as well. By setting up substitute on a counter switch, you have a free turn to either set Cruel up, or punish with a respective super effective attack. Here are a few sample sets.
-Substitute
-Hydro Pump
-Mega Drain
-Confuse Ray / Toxic
The last option is for your enfeebling move of choice. Tox can be a great option against Chansey, or any other special attacker that Tentacruel can shrug off.
Another option is to utilize Swords Dance for a surprise attack.
-Substitute / Barrier / Reflect
-Swords Dance / Screech / Hydro Pump
-Hyper Beam / Double Edge
-Acid / Confuse Ray
Now you might say, why in the F*** would I use acid. The answer is that not much of the meta resists it, and those that do can usually be punished with Hydro Pump. STAB-boosted Acid after a swords dance may even do decent damage to Haunter. The possibility of lowering defense is another plus that may force switches. Could run alongside Screech well.
-Substitute
-Hydro Pump
-Mega Drain
-Confuse Ray / Toxic
The last option is for your enfeebling move of choice. Tox can be a great option against Chansey, or any other special attacker that Tentacruel can shrug off.
Another option is to utilize Swords Dance for a surprise attack.
-Substitute / Barrier / Reflect
-Swords Dance / Screech / Hydro Pump
-Hyper Beam / Double Edge
-Acid / Confuse Ray
Now you might say, why in the F*** would I use acid. The answer is that not much of the meta resists it, and those that do can usually be punished with Hydro Pump. STAB-boosted Acid after a swords dance may even do decent damage to Haunter. The possibility of lowering defense is another plus that may force switches. Could run alongside Screech well.