Sentry

 

Securely

Like two peas in a pod.   Romeo loved his daddy.  As seen in 2017.

Formidability

 

Ternary

Three seasons in one image: summer flowers, autumn leaves, and winter snow.  

The flowers are so pretty that I had to research what kind of plant it is.  And of course, it is a weed.  Linaria vulgaris, otherwise known as "Butter and Eggs" or "Yellow Toadflax."  But I still think it's pretty.  And it's hardy enough to withstand some winter weather.

Oppositionary

 Autumn and winter have been warring with each other for the past week.