SSBU/Pichu/Combos

Edgeguard
Pichu excels at edgeguarding.

Its long-lasting multihits: bair and fair, can cover a large area in a sweeping motion. Thunder can cover low and high recoveries simultaneously if the Pichu player reads the drift in timing. Fastfall double jump Thunder is especially good at covering jump-ins after threatening covering low. Nair can be used to cover the area right in front of the ledge when dealing with recoveries without a hitbox(think of it as a meta-knight nair). Downair is a superb edgeguarding move as its hitbox covers pichu entierly, lasts very long and the sourspot is a strong launcher that sends sideways, so most of the time the sourspot will kill regardless. Instant runoff dair covers really well dropzone recoveries that have a bit of startup (think of wolf recovery) Instant runoff bair (facing towards the stage) is one of the strongest tools pichu has for gimping. Bair threatens a stage spike if not dragged-down, and will instantly kill most if not all characters if an airdodge is buffered to get the stage spike tech but the bair is dragged down instead. It constitutes a heavily Pichu favored 50%-50% that kills most characters on the spot. Tjolt can be used from the stage to cover linear recoveries such as falcon's, ganon's etc, and it sets up perfectly for any aerial from above. Given all the tools Pichu has offstage, faking an edgeguard with a quick jump offstage and back to the ledge, letting people panic and punishing with ftilt from the corner or bair to cover risky high recoveries can prove really effective.

Ledgetrap
Pichu's ledgetrapping cornerstone is its ability to hit below the ledge extremely quickly as invincibility runs out with ftilt (or even dtilt situationally), or cover that position preentively with long lasting multihits like fsmash or dsmash.

The threat of fast, threatening options as soon as invincibility runs out forces quick ledge options from the opponent, which can be exploited fairly easily.

Pichu is fast enough to cover most rolls starting at neutral getup distance with a dash in into imagination (mostly ftilt at high % for a safe hit to reset to edgeguard or uptilt at low %'s to start combos). Ledgejump is easily covered with fullhop bair on reaction or even can be thrown out half a second before the timing you are expecting which still covers the jump and lets you reset to roll distance and even hit back to ledge some players trying to roll past the bair on reaction (if the bair was faded back and with a shorthop) Fsmash proves a really good neutral getup punishing tool, being so long lasting that most of the time it catches neutral getups even if it is started as soon as the neutral getup animation starts. Tjolt forces players to choose an option immediately, most of the time neutral getup, which can be punished with long-lasting hitboxes as mentioned. Trumping into bair or fastfall upair into thunder can also be a good option to punish overpatient players.