About Juggernaut

[Uicheusa]

Can it be charged while the character is being stunned/paniced/etc. if it has the 'unstoppable' upgraded?

[Crowsfoot]

Nope

[Drearivev]

When you're stunned/under panic, you can't charge anything. The Unstoppable upgrade just allows you to not get any movement impairing effect (stun, snare etc.) after you used Juggernaut.