Simple Squash Stretch, can be used for pretty much anything. (Celeste-like effect)

SimpleSquashStretch.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class SimpleSquashStretch : MonoBehaviour {
  
  public Vector3 wallSquash = new Vector3(1.66f, 0.7f, 0.1f);
  public Sprite m_SpriteRenderer;
  
  void Start()
  {
      //Example
      StartCoroutine(JumpSqueeze(wallSquash.x, wallSquash.y, wallSquash.z, true));
  }

  IEnumerator JumpSqueeze(float xSqueeze, float ySqueeze, float seconds, bool isInstant)
    {
        Vector3 originalSize = Vector3.one;
        Vector3 newSize = new Vector3(xSqueeze, ySqueeze, originalSize.z);
        float t = 0f;
        if (isInstant == false)
        {
            while (t <= 1.0)
            {
                t += Time.deltaTime / seconds;
                m_SpriteRenderer.transform.localScale = Vector3.Lerp(originalSize, newSize, t);
                yield return null;
            }
            t = 0f;
        }
        while (t <= 1.0)
        {
            t += Time.deltaTime / seconds;
            m_SpriteRenderer.transform.localScale = Vector3.Lerp(newSize, originalSize, t);
            yield return null;
        }

    }

}