。
I support you wholeheartedly.
Literal
I [topic-は] you [object-を] completely support.
全面的に (ぜんめんてきに, 'completely, wholeheartedly, across the board') — the な-adjective 全面的 in adverbial に form. 支持する (しじ, 'to support, back, endorse'). A strong declaration of support.