Resume wording
"Strengthened" gives no baseline and no direction. Strengthened from what, to what? Without a number it reads as a claim the reader is asked to take on trust, which is exactly what a resume cannot afford.
These are not interchangeable. Picking the wrong one is how a bullet ends up claiming something you did not do, so the second column matters more than the first.
Before
Strengthened the deployment process.
After
Hardened the deploy pipeline with automated rollback, cutting failed releases from 1 in 6 to 1 in 40.
The verb is the smaller half of that change. What actually makes the second version work is the number, and no synonym can supply one for you.
Keep "strengthened" for relationships and partnerships, where "hardened" or "tightened" would read as adversarial.
Rewriting one bullet is easy. Rewriting forty against a specific job posting is the part people give up on. Tailor CV rewrites your resume against the posting you are actually applying to, and you edit what it gives back.