Hello Neighbor

Beat the Giant Neighbor Boss in the Finale Act. You need to complete Acts 1, 2 and 3 then beat the final boss. General game tips – is running. Will help to escape Neighbour (needed at tunnel segment of Act 1) and for long jumps (run then jump) to make gaps. You can jump stack boxes (stand on a box, jump, place with and repeat. In act three always have an umbrella and make sure opened with . Running across the road to the ground of ‘your property’ will stop Neighbour’s chasing. Breaking windows will always get Neighbour’s attention so only causes more problems if just entering the house from ground level. Make sure in the options that 'Friendly Neighbor' is turned on.

Act 1 – Get the car key from the upstairs room. Get the magnet from the car trunk. Use it to grab a lockpick from the back storage room through the vent. Use the lockpick on the silver lock to get the crowbar from the storage room. Unlock the gate at the back of house, use ladder to reach roof then drop down to get red key. Use key on red lock in house to enter basement.

In the basement unblock doors by removing chairs. Flip all gates, then return to starting room to flip power box lever. Run through unlocked rooms to press button on generator, then flip the powered switch to go through door.

Video Game News has a speedrun guide to Act 1 here:

Act 2 – Look through keyhole until you hear noise. Look at knocked over window to hear door unlocking so you can leave. Remove grate and go through vent to reach room with ladder to climb out to new, fenced off Neighbour house. Get wrench from kitchen and use on gate outside to access ladder. Flip all three orange pipe switches, then use red valve on all three red points on pipe to drain water, including by boiler in side room that you need to hit switch. Climb up side tower, go through drained room, go down ladder, then downstairs to use valve on pump and activate. Jump from rook by ladder at front of house to use trampoline to escape.

“Harley Quinn” has a video guide for the trampoline route:

Act 3 – To properly complete Act 3 you need to do several steps including unlocking doors and locks, and powering up the tram of the railroad around the outside of the house. Ultimately you need to remove the chair from in front of the basement door, use a crowbar to remove the boards in front of it, and defrost the blue keycard to use on the reader to open the door. However you'll also need to complete the three 'fear' rooms for powers you need to beat the final basement. However in this Act, you'll want to complete the "Shoot'em Up" achievement plus the miscellaneous achievements for finding landmarks, getting the Golden Apple, etc. before you beat the basement.

Video Game News has a guide to beating Act 3 (including all the ‘fear’ rooms) and the Finale Act (but doesn’t show the steps for getting the gun etc):

The basement is different than Act 1, but to complete it needs all 3 ‘powers’ you gained through the ‘fear’ rooms. Crouch to head through the washer door, but in the fake room beyond head through the dark gap to the left. Go past the open gate and the TV. At the end of the corridor crouch to hide as the creature passes, then head on. At this new section go through the door, burst the brick section with a thrown chair, and in the next area double jump over the fence into the gap. Open the door, and mash to escape the Neighbor. Run through and reach the far door, and crouch to enter.

Boss time! From the platform once you’re free from the room head right to double jump up the metal platforms and press the red button to send the cart moving to open up a house for later. Grab boxes and flip switch on the big green wall behind the starting platform, and keep one box with you. Head around it and jump from the top of torch to the radio, then up the antenna to the shelf to jump into the toaster. Push forward so at the top you’ll land on a higher platform with a switch. Flip it, turn around and drop down to platform below then quickly run jump onto the moving platform. Break window at the top and flip switch in room. If you can grab an umbrella as you fall, or just grab one off the ground when you respawn.

If you caught an umbrella mid-fall (or use the toaster to boost) use it to glide into the house we opened up before (it’s to the right of the Neighbor) and grab a candle off the cake. Glide to the ground and use the candle to light the fuse of the firework on the ground in front of the starting platform. Next toaster boost to land on the shelf on the green wall with a mint packet to pick up a mint. Glide back to the toaster and glide across to the far shelf with baseballs on it. Roll one into the practice machine to shoot the Neighbor. From this platform run jump and glide across to the far green platform and burn the rope with the candle to shoot the dart.

Back to the toaster, and this time land on the top of the red stack of chairs on the right of the green wall. Use the mint on the cola bottle to send it flying, then back to the toaster to glide to the gramophone. Throw a box at the lever to lower it, then get the disc rotating by running clockwise around the top a couple times. From the gramophone glide across to the far blue platform by the house and from there jump to the porch on the house on Neighbor’s back and enter (you can toaster glide if you miss the jump first time). The achievement will unlock in the next section.

The achievement was previously glitched (would not unlock after beating) but is fixed by version 1.0.0.8 patch.