Locking opponents out of the game is a truly game-breaking effect, and it led to what many consider a controversial ban in Commander in 2019 when Painters Servant was unbanned
Rather, it was more an effect of availability
Double Strike + Deathtouch Double strike plus deathtouch allows a creature to instantly destroy any creature it deals damage to in the first combat step before the blocking creature has a chance to deal any regular damage itself
At the beginning of each combat, you may attach target Aura or Equipment attached to a creature you control to target creature you control
(on a huge creature with trample, for example) I know some players would say Pariah's Shield is a better play as it's harder to remove and that is true but it costs more and that is the only reason I'm not using it
Fetchlands This may be an obvious choice but I think the Onslaught fetchlands are important not only for Modern and Legacy, but also for Standard