Tank cat is the second cat you unlock playing the main chapters. It is primarily used as a short range small spammable tanker, its useable through the entire game and rarely replaced. Its true form eraser cat gains more attack and defense.

Evolves into Wall cat at level 10

Evolves into Eraser cat at level 30(20+10)

EOC

In Empire of Cats tank cat is mainly used to support close ranged attackers like Titan cat or Fish cat. It is useful during the entire set of chapters ad can not be realistically subbed out. Tank cat is very useful again the Moon bosses because it can absorb attacks allowing units such as Dragon cat or Gross cat to get extra hits in.

ITF

In Into the Future tank cat and its true form is used as a high grade meatshield to protect from attacks. This cat can be used to protect Bahamut cat or any other attacker from ranged enemies such as Maawth or I.M Phace. In the moons it can be useful against everything especially Raging Bahamut Cat.

COTC

Cats of the Cosmos gets more complicated due to the restrictions on your loadout. In normal only stages or for that matter every stage where its available, tank cat should be used for meatshielding all the time. Especially on Big Bang or Triton.

Basic cat is a great early-mid game meatshield that can be used to block enemy attacks, protecting your damage dealers. This is the first cat you unlock in the game and can be useful throughout. The true form Mohawk Cat increases health and damage by double

Evolves into Macho Cat at level 10

Evolves into Mohawk Cat at level 30 (20+10)

EOC

In Empire of Cats basic cat in all of its forms are useful. The first chapter (The battle cats rising) it can be used as a damage dealer for the first few levels and can be used as a damage absorber around halfway in, the second chapter makes Cat less of a necessity but can help in levels like Moon and Alaska. The last chapter in empire of cats (Revival Of Bahamut Cat) makes cat even less needed with a few exceptions eg. Moon and Hawaii.

ITF

In Into the future basic cat is good for meatshielding and nothing else with a few exceptions. Time enough for cats is fairly simple and can be compared to EOC 3 but there are some levels where cat shines like Moon or the early levels. By ITF 2 you should have Bahamut cat which can be protected by basic cat. By mid ITF 2 crazed cats start to replace basic cat and it becomes more useless in Ancients Arise

COTC

In cats of the cosmos the loadout is limited thanks to restrictions. Basic cat can be useful in normal cat restrictions and that’s pretty much it because it gets replaced by M. Mohawk and the other meatshields.