I'd be underestimating you'd be underestimating she'd be underestimating we'd be underestimating you'd be underestimating they'd be underestimating
Perfect
I should've underestimated you should've underestimated she should've underestimated we should've underestimated you should've underestimated they should've underestimated
V-ing perfect
I should've been underestimating you should've been underestimating she should've been underestimating we should've been underestimating you should've been underestimating they should've been underestimating
Negation
Simple form
I shouldn't underestimate you shouldn't underestimate she shouldn't underestimate we shouldn't underestimate you shouldn't underestimate they shouldn't underestimate
V-ing form
I shouldn't be underestimating you shouldn't be underestimating she shouldn't be underestimating we shouldn't be underestimating you shouldn't be underestimating they shouldn't be underestimating
Perfect
I shouldn't have underestimated you shouldn't have underestimated she shouldn't have underestimated we shouldn't have underestimated you shouldn't have underestimated they shouldn't have underestimated
V-ing perfect
I shouldn't have been underestimating you shouldn't have been underestimating she shouldn't have been underestimating we shouldn't have been underestimating you shouldn't have been underestimating they shouldn't have been underestimating
Interrogative form
Simple form
should I underestimate? should you underestimate? should she underestimate? should we underestimate? should you underestimate? should they underestimate?
V-ing form
should I be underestimating? should you be underestimating? should she be underestimating? should we be underestimating? should you be underestimating? should they be underestimating?
Perfect
should I have underestimated? should you have underestimated? should she have underestimated? should we have underestimated? should you have underestimated? should they have underestimated?
V-ing perfect
should I have been underestimating? should you have been underestimating? should she have been underestimating? should we have been underestimating? should you have been underestimating? should they have been underestimating?
Interro-negative form
Simple form
shouldn't I underestimate? shouldn't you underestimate? shouldn't she underestimate? shouldn't we underestimate? shouldn't you underestimate? shouldn't they underestimate?
V-ing form
shouldn't I be underestimating? shouldn't you be underestimating? shouldn't she be underestimating? shouldn't we be underestimating? shouldn't you be underestimating? shouldn't they be underestimating?
Perfect
shouldn't I have underestimated? shouldn't you have underestimated? shouldn't she have underestimated? shouldn't we have underestimated? shouldn't you have underestimated? shouldn't they have underestimated?
V-ing perfect
shouldn't I have been underestimating? shouldn't you have been underestimating? shouldn't she have been underestimating? shouldn't we have been underestimating? shouldn't you have been underestimating? shouldn't they have been underestimating?