vs
QUICK ANSWER
"Ladera" is a form of "ladera", a noun which is often translated as "slope". "Pendiente" is an adjective which is often translated as "pending". Learn more about the difference between "ladera" and "pendiente" below.
la ladera(
lah
-
deh
-
rah
)A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
1. (general)
b. hillside 
Decidimos no montar la tienda de campaña en la ladera.We decided against pitching the tent on the hillside.
c. mountainside 
Seguí el arroyo que bajaba por la ladera.I followed the stream that ran down the mountainside.
pendiente, la pendiente(
pehn
-
dyehn
-
teh
)An adjective is a word that describes a noun (e.g., the big dog).
1. (unresolved)
b.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
¿Solucionaste todo o quedó algo pendiente?Did you sort everything out or is there still stuff to do?
Volvimos a hablar, pero todavía hay algunos asuntos pendientes.We started talking again, but there are still some issues to sort out.
3. (attentive)
a.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
Estaban pendientes de noticias del pueblo después del tornado.They were waiting on news from the town after the tornado.
Estaremos pendientes de tu hijo.We'll keep an eye on your son.
4. (inclined)
A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
A masculine noun is used with masculine articles and adjectives (e.g., el hombre guapo, el sol amarillo).