Also you're obviously an antisemite.
But, yes, the main reason I ranked Russian #1 is that there are many very large very populous countries with a lot of people who understand Russian but not English.
If you speak one Slavic language, others are relatively easy. Slovak, Ukrainian, Polish, Czech are pretty similar. My Slovakian and Polish colleagues at work can talk to each other in their own language and the other person will understand, same with Slovak and Czech.