What are you most looking for from vendors that pitch you?

All of the following:
1. A demonstrated understanding of my specific challenges, industry, and goals.
2. A clear value proposition
3. A track record of credibility/trustworthiness (and if we have no history, references from my same industry)
4. Consistent, reliable, professional communication

I'd say transparency and sincerity. These, in my estimation, will determine if I will trust you or not. Once the trust is established, it's all about negotiations and making sure you aim for a win-win strategy that will ensure a sustainable partnership.

Authenticity.  Be real. After 35 years i’m business Be Real.  It wont all be sunshine and rainbows. 

No BS, I have developed over the years of being on both the buy side ( CFO / COO ) and sell side ( DXC technology, SAP and Workday) a quite good BS meter. 
Oh and being Australian i have the luxury of growing up in a culture that calls BS out , even with your mates.

I'm looking for vendors that demonstrate an extended "ownership culture".  Don't get greedy with pricing, don't start off low and inflate prices over time, don't overpromise and underdeliver.  Look for opportunities to help me demonstrate value to the business, and be a partner in my success as I deliver that value into the organization.  Too many vendors want the deal, but not the work involved in creating value after the ink is dry.

I think it depends on the software or service that I am looking to purchase.  But one thing that remains universal is an easy buying process.  No, I don't want 45 meetings to buy a calendaring tool.  No I don't want a demo for a software I have used at 3 previous roles but because it is part of your "process" I have to book one.
I think that many companies should be cognizant of their customer journey rather than what they prefer.  It's not about info dumping, it is about meeting your buyer where they are at in their own journey and adjusting your process to fit that.
Other than that, communication is key!