Xiaoqiang: specifically refers to cockroaches, and by extension refers to those characters that are difficult to kill. (The devil in the game, the protagonist, etc.)
Da Qiang: A character that is more difficult to kill than Xiao Qiang.
The word "Xiaoqiang" comes from Stephen Chow's famous work "Tang Bohu Spots Autumn Fragrance", in which he named a passing cockroach "Xiaoqiang", and the use of "Wangcai" to refer to dogs in general also comes from Xingye's drama.