User blog comment:Godisme/San'ou/@comment-5053144-20120726104608/@comment-44061-20120726121549

We dont even know the significance of the "5 war potentials" considering that the orders were to kill ichigo they are important to the Vandenreich. Though considering they attacked Soul Society when Ichigo was busy in Heuco Mundo, the Vandenreich obviously fear the interference of a war potential. So they want them dead cause they are dangerous to their plans. If thats the case then why attack when one is exactly where you going, when your whole point of attacking is because one was preoccupied somewhere else. Defeats the purpose and doesnt make much sense. Also the Vandenreich leader looks similar to Zangetsu meaning kubo used the same template which he has increasingly done with multiple characters. Also it makes no sense for him to be afraid of Zangetsu, for all anyone knows besides Yoruichi, Zangetsu is just the name of ichigo's sword. No one can see the spirit itself but Ichigo. Zangetsu came into existence with ichigo's shinigami powers cause he is part of ichigo's soul. What you imply is a prior relationship or acknowledgement of spirit which is impossible in content of the story.

There is no fear of bankai or the spirit. His only issue is that Ichigo is a problem for him because he interfers with his plans.