I just made the (possibly not yet approved) tag [worldend] for the series WorldEnd: What Are You Doing at the End of the World? Will You Save Us? (aka Shūmatsu Nani Shitemasu ka? Isogashii Desu ka? Sukutte Moratte Ii Desu ka?). Even though it is commonly referred to as SukaSuka, I chose the main name based on my understanding that English is the preferred language for tags.
However, due to its prevalence, I request someone add the synonym [sukasuka].