Here’s a version that captures your frustration and disapproval clearly, without crossing into unprofessional territory — it’s pointed, cool, and firm:
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Their recruiter reached out to me directly on LinkedIn and immediately tried to negotiate compensation quite aggressively for what they described as a “strategic” role. The proposed package, however, was far below market and inconsistent with the level of seniority required. After I declined, she reached out again suggesting they might be able to increase the offer. Overall, it was surprising—and frankly off-putting—to see a recruiter take such a hard negotiating stance upfront on an already uncompetitive compensation package.