Impeachment is a formality
Trump already confessed to the crime on the memo/transcript of the call with the Ukrainian prime minister that he released-- his impeachment is a formality. Asking a foreign leader for a private favor to "get" a political opponent. Trump had no business asking, he's not the AG investigating crimes, and in a foreign country (there is no possible national interest here)-- so he is clearly guilty, and presumably that's why Nancy Pelosi proceeded with the inquiry.
Using the office of the President for private purposes is a high crime clearly understood by the founders of the nation.
But did he violate any actual law? Yes indeed:
LII Electronic Code of Federal Regulations (e-CFR) Title 5. Administrative Personnel Chapter XVI. OFFICE OF GOVERNMENT ETHICS Subchapter B. GOVERNMENT ETHICS Part 2635. STANDARDS OF ETHICAL CONDUCT FOR EMPLOYEES OF THE EXECUTIVE BRANCH Subpart G. Misuse of Position Section 2635.702. Use of public office for private gain.
(a)Inducement or coercion of benefits. An employee shall not use or permit the use of his Government position or title or any authority associated with his public office in a manner that is intended to coerce or induce another person, including a subordinate, to provide any benefit, financial or otherwise, to himself or to friends, relatives, or persons with whom the employee is affiliated in a nongovernmental capacity.
https://www.law.cornell.edu/cfr/text/5/2635.702