せいで

The expression せいで attaches to a cause that leads to a negative result. It often carries blame or fault attribution, meaning the following outcome happened due to that cause. It is commonly used with concrete causes like weather, health, or someone’s actions. When you attach the cause to a noun, you typically use のせいで; with verbs or adjectives you attach せいで directly to the plain form (past for actions that already occurred). The nuance is that the speaker sees the cause as responsible for the unwanted outcome.