Everyone, I'll be backing you up with everything I've got too. We're absolutely going to make this event a success.
Literal
Everyone, I [also-も] full-power [with-で] follow-up do. This event definitely succeed-[causative-させる] [emphatic-ぞ].
An enthusiastic rally cry. 全力でフォローする ('to follow up / support with full power') uses the loanword フォロー in its Japanese sense of 'backing up, supporting' — not the social-media 'follow.' 成功させる is causative: 'to make succeed' — taking active responsibility for the outcome. かならず ('definitely, without fail') and the masculine ぞ ending project unwavering determination.