This study examines the “political grammar” of President Yoon Suk Yeol, extending the concept of grammar from linguistic rules to political norms. Using a corpus of 3.397 billion words from political news articles (1990-2025) and 6.137 million words from presidential speeches (1948-2024), the analysis integrates frequency, TF-IDF, collostructural analysis, word-embedding, text summarization, and sentiment analysis. The findings reveal striking lexical anomalies, including the rapid diffusion of neologisms and idiosyncratic coinages. Unlike earlier presidents, whose adversarial rhetoric targeted external enemies, Yoon consistently redirected “war” frames toward domestic rivals. Sentiment analysis further highlights the exceptional prominence of solemnity and hatred, peaking in the August 15, 2023 Liberation Day address and the December 3, 2024 martial law proclamation. These patterns indicate not a transient rhetorical effect but a structural transformation of South Korea's political discourse. By institutionalizing negative effects and dehumanizing frames, Yoon's political grammar demonstrates how democratic language can be reshaped into tools of antagonism, with profound implications for the health of deliberative democracy.