What is the standard for making a "clear showing" of oppression and vexation of a defendant in a civil case?

The standard to be applied is whether, in light of these factors, defendants have made a "clear showing" that either: "(1) establish such oppression and vexation of a defendant as to be out of proportion to the plaintiff's convenience, which may be shown to be slight or nonexistent, or (2) make trial in the chosen forum inappropriate because of considerations affecting the court's own administrative and legal problems." Id. at 670 (quoting Hoffman v. Goberman, 420 F.2d 423, 426-27 (3d Cir. 1970)).